Add 7 new difftests and push constants support

New tests:
- bitwise_ops: bit manipulation operations
- trig_ops: trigonometric functions
- control_flow_complex: nested loops and complex control flow
- vector_swizzle: vector component access and swizzling
- memory_barriers: workgroup memory synchronization
- vector_extract_insert: dynamic vector element access
- push_constants: push constants in compute shaders

Infrastructure changes:
- Add WgpuComputeTestPushConstants for push constant support
- Enable PUSH_CONSTANTS feature in wgpu when needed
- Register all existing unregistered tests in workspace

Author: LegNeato

tests/difftests/lib/src/scaffold/compute/mod.rs

@@ -1,2 +1,5 @@
 mod wgpu;
-pub use wgpu::{RustComputeShader, WgpuComputeTest, WgslComputeShader};
+pub use wgpu::{
+    BufferConfig, BufferUsage, RustComputeShader, WgpuComputeTest, WgpuComputeTestMultiBuffer,
+    WgpuComputeTestPushConstants, WgslComputeShader,
+};