Reduce Animate shape command memory usage

[Tutez64]

Summary

This changes how Animate shape commands are stored at runtime:

• keep parsed commands in a compact numeric representation instead of eagerly
  allocating one AnimateShapeCommand enum object per drawing command;
• render compact commands directly into Graphics when a shape is first
  instantiated;
• cache the rendered graphics and release the compact command data afterward;
• preserve the existing public commands path for manually constructed
  AnimateShapeSymbol instances;
• add a regression test comparing compact rendering with the legacy command
  representation.

Motivation

Animate exports already represent shape commands as flat JSON command streams.
AnimateLibrary currently expands every stream while loading into enum objects,
matrices and nested arrays, even for shapes that are never instantiated.

Large Animate libraries can therefore retain hundreds of thousands of managed
objects. Besides the additional memory usage, these objects increase the live
graph that hxcpp must traverse during garbage collection, resulting in longer
GC stalls as more assets are loaded.

The new representation keeps the command stream compact and delays graphics
creation until the shape is actually used.

Benchmark

SWFAnimateShapeCommandMemoryRepro.zip
It parses and retains 1,000 unrendered shapes containing
1,050 commands each.

Results on Linux x86_64 with Haxe 4.3.6 and HXCPP_GC_BIG_BLOCKS:

Metric	master	This PR
Parse time	119–140 ms	59–69 ms
Retained hxcpp heap	107.6 MiB	31.8 MiB
First full GC	13–14 ms	0–1 ms
Median forced compacting GC	28–31 ms	0–1 ms

Real-world validation

Metric	Before	This PR	Change
Surviving AnimateShapeCommand instances	759,391 (~52 MiB shallow)	0	eliminated
Non-full-scan GC pause, median	58.30 ms	37.65 ms	-35%
Non-full-scan GC pause, p95	69.11 ms	50.17 ms	-27%
Non-full-scan GC pause, maximum	84.67 ms	66.60 ms	-21%
Mark phase, median	51.33 ms	32.56 ms	-37%
Peak live hxcpp heap	824.6 MiB	767.6 MiB	-7%

These values should be considered indicative rather than a controlled benchmark.
However, the complete removal of roughly 759,000 surviving command objects,
together with consistently shorter marking and GC pauses, confirms that the
improvement also applies under a real game workload.

The patched run completed normally with no visible shape rendering regression.

Related change

This PR has a small textual overlap with #54, which adds
lineGradientStyle support. The changes are functionally independent, but both
modify AnimateLibrary.hx and AnimateShapeSymbol.hx.

Once either PR is merged, I can rebase the other one. The combined resolution
handles LINE_GRADIENT_STYLE through the same compact gradient command path and
calls Graphics.lineGradientStyle while rendering. This combined version has
already been tested downstream.

[Tutez64]

The new Animate shape test caused AnimateTimeline to be compiled on Haxe 3.4.7, exposing a pre-existing parser incompatibility in a combined conditional expression. The condition has been split into nested directives in both the Animate and SWFLite timeline implementations.