.aep import: effects without definitions borrow them from another instance (#3223)

Refs #3170 (the Color Control part).

Some files have no project-level effect definition list (EfdG); it was seen in
17 projects, all from inside After Effects-made Motion Graphics templates. In
those, one instance per effect type keeps the full parameter definitions
(parT) and every other instance of the type has an empty parT. The others
were reported "without readable parameter definitions" and dropped (129
Color Controls of one template). The definition index now falls back to the
parT of the first instance of the same match name that has its own
(DefinitionSource::OtherInstance). Values still come from each instance's own
records; a value record that borrowed definitions do not name is reported
instead of vanishing.

The "Color ... holds an unreadable value" report came from 0.21.1, which read
only written records (tdsb 1). Reading default-state records (tdsb 3, #3126)
probably fixes it, but that is not confirmed for Color Control; a synthetic
test now pins a default-state colour record.

docs/aep-format.md

@@ -461,7 +461,7 @@ The expression engine is project-wide (`LIST ExEn/Utf8`, `javascript-1.0`). API:
 | **default** | `pard` | 56 | by type | float slider: f64 (Slider 0, **Blurriness 25**); fixed slider and angle: 16.16 (drop shadow opacity 127.5, direction 135, distance 5, softness 0; Fill opacity 1.0 = 100 %; **Tint Amount to Tint 100, Ramp Scatter 0, Blend With Original 0**); **colour: ARGB bytes (drop shadow `ff000000` black, Fill `ffff0000` red; Ramp Start `ff000000`, End `ffffffff`; Tint Map Black To `00000000` and Map White To `00ffffff`: alpha 0, which is what After Effects reads back)**; popup: u32 index (1); **point: two 16.16 fractions of the layer size at 56 and 60 (Point Control 0.5, 0.5; Ramp Start 0.5, 0 and End 0.5, 1)** | 071, 077, 080, 214, 215, 356, 368, 383 | V |
 | **valid maximum** | `pard` | 128 / 108 | 16.16 / f32 | the largest valid value of a fixed slider (128: Tint Amount 100, Ramp Scatter 512, Blend With Original **1.0**) and of a float slider (108: Blurriness 30 000; **Exposure 100, Offset 2, Gamma Correction 10**). The stored scale differs per slider (below), so this is the reader's only hint at it | 356, 368, 078, 389 | V |
 | **float slider valid minimum, slider range** | `pard` | 104; 112 / 116 | f32; f32 x 2 | the smallest valid value (Exposure -100, Offset -2, Gamma Correction 0.1 as f32) and the range the slider covers (Exposure -4..4, Offset -0.5..0.5, Gamma 0.1..10); the slider range is repeated as `tdum` / `tduM` (f64) in each value record (391-394). @120 holds the default again as f32 (Gamma 1.0, Blurriness 25), u16 @124 the display decimals (**H**: Exposure 2, Offset 4) | 389, 391-394 | V |
-| **definitions of a second instance** | top-level `LIST EfdG` | | | one `EfDf` per effect TYPE (`tdmn` = match name, then a copy of ONE instance's `sspc`, including that instance's value records); the `EfDC` count before them is a little-endian u32. When two layers carry the same effect type, only one instance keeps a full `parT`; **the other has an empty `LIST parT` (4 bytes)** but its own `tdgp` (input layer `-0000` with its own `tdpi`, the button record, and its value records). Its definitions come from the `EfdG` copy by match name, its values from its own records, never from the copy (383: the copy holds S100's Start [0.1, 0.2]; L's Ramp reads the 368 defaults). Which instance keeps the full `parT` is **?** (in 383 S100 is both first in the file and newest). The `EfDf` order follows the stack order (365 / 366); `Pefl/pjef` does not | 365, 366, 383 | V |
+| **definitions of a second instance** | top-level `LIST EfdG` | | | one `EfDf` per effect TYPE (`tdmn` = match name, then a copy of ONE instance's `sspc`, including that instance's value records); the `EfDC` count before them is a little-endian u32. When two layers carry the same effect type, only one instance keeps a full `parT`; **the other has an empty `LIST parT` (4 bytes)** but its own `tdgp` (input layer `-0000` with its own `tdpi`, the button record, and its value records). Its definitions come from the `EfdG` copy by match name, its values from its own records, never from the copy (383: the copy holds S100's Start [0.1, 0.2]; L's Ramp reads the 368 defaults). Which instance keeps the full `parT` is **?** (in 383 S100 is both first in the file and newest). The `EfDf` order follows the stack order (365 / 366); `Pefl/pjef` does not. **Some files have no `EfdG` at all** (seen in 17 projects, all from inside After Effects-made Motion Graphics templates). In each of them every effect type (196 in all; 2 to 14 Color Controls per file) has exactly one instance with a full `parT` and an empty one in every other instance, and the reader takes the others' definitions from that instance (`DefinitionSource::OtherInstance`, #3170). Which instance keeps it is **?** here too | 365, 366, 383; templates | V |
 | popup items | `parT/pdnm/Utf8` | | text | items separated by `\|` | 077 (`Item 1\|Item 2\|Item 3`), 214 | V |
 | stored value | `sspc/tdgp/<match>-NNNN` | | `tdbs` | present only for a parameter that differs from its default; `tdsb` 1, `cdat` as in 3.4. **Absent record = the `pard` default.** Some parameters are recorded in the default state (`tdsb` 3) and the record still holds the value After Effects uses: every one of the 25 such records in the corpus and the samples differs from its `pard` default and reads back as recorded (Lumetri Color's hidden controls High Dynamic Range, HDR Specular, the second Look, Legacy Tone And Saturation, Face Detection, Auto Color, Auto Intensity and SemanticAutoTone Progress, 1200; Cryptomatte's Selection Mode on, 1400). No effect record in the default state holds a value that does not count. The reader takes the value in either state (`EffectParam::recorded_value`, `EffectParam::value`); `EffectParam::stored_value` keeps to written records, and a record in any other state (no sample has one) is not read: the importer reports it as damaged data. That other effects record values so is H (no sample shows one) | see below; 1200, 1400 | V (1200, 1400), H (other effects) |