migrate wan vace lora tests to the pipeline-level mixins

[akshan-main]

What does this PR do?

Migrates the Wan VACE pipeline LoRA tests from tests/lora/test_lora_layers_wanvace.py to the pipeline-level mixins from #14268, same shape as #14613: TestWanVACEPipelineLoRA(WanVACEPipelineTesterConfig, LoraTesterMixin) and TestWanVACEPipelineLoRAMemory(WanVACEPipelineTesterConfig, LoraMemoryTesterMixin) in tests/pipelines/wan/test_wan_vace.py, and the old file removed.

The VACE-specific exclude_modules test is ported as a method on the new class (targets proj_out while excluding vace_blocks.0.proj_out, with the save/load round-trip checks). The old file's other specifics dissolve the same way as in #14613: text-encoder tests skip through _lora_loadable_modules, the block-scale skips disappear with UNetLoraTesterMixin, and the tolerance overrides are not needed at the mixin defaults. Follows #14613.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline?
• Did you read our philosophy doc (important for complex PRs)?
• Was this discussed/approved via a GitHub issue or the forum? Discussed on Slack with @sayakpaul
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Who can review?

@sayakpaul

[sayakpaul]

/diffusers-bot pytest tests/pipelines/wan/test_wan_vace.py -k "lora"

[github-actions]

✅ pytest tests/pipelines/wan/test_wan_vace.py -k "lora" passed on GPU — view logs.