webgpu: Cover immediate data in indirect commands

Exercise indirect compute dispatch and indexed/non-indexed rendering with immediate values in compute, vertex, and fragment shaders. Cover repeated commands, mixed direct/indirect commands, partial updates, bundle isolation, and multi-draw count buffers using the existing execution helpers.

Presubmit passes, including 1031 framework unit tests. D3D12 runs in core and compatibility modes pass the new rendering cases and reproduce immediate-data corruption in indirect compute dispatch.

Author: shaoboyan091