[TreesInViz] Test: Validate animation keyframe type consistency

Improve animation keyframe validation in `LayerContextImpl` by
ensuring `AnimationKeyframe.value` types are consistent.

The 1st key frame type determines the type of the key frame curve.
If subsequent key frames have a mismatched type, we return a new
specific "Invalid keyframe type" error.

The change adds several tests, with different mismatched types:
ScalarToTransform, ColorToOpacity, and RectToBackgroundColor.

Bug: 425371474
Change-Id: I13cb15d6a9d27dffbd80702d4a3374ba0f0576b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6648010
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Commit-Queue: Victor Miura <vmiura@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1475107}