[WGSL] override expressions as array lengths do not compile

[Mike Wyrzykowski]

Running the following CTS test:
  https://gpuweb.github.io/cts/standalone/?q=webgpu:api,validation,compute_pipeline:overrides,workgroup_size,limits,workgroup_storage_size:isAsync=true

We see the error:
  1 error generated while compiling the shader:
  5:45: array count must evaluate to a constant integer expression or override variable

--------------- Shader source ---------------

              override a: u32;
              override b: u32;
              
              var<workgroup> mat4_data: array<mat4x4<f32>, b>;
              @compute @workgroup_size(1) fn main() {
                
                _ = mat4_data[0];
              }
--------------- end shader source ---------------

We can use function constants inside the generated metal shading language array length declaration.

[Radar WebKit Bug Importer]

<rdar://problem/121971104>

[Tadeu Zagallo]

Pull request: https://github.com/WebKit/WebKit/pull/23972

[EWS]

Committed 274296@main (2e6c189562a8): <https://commits.webkit.org/274296@main>

Reviewed commits have been landed. Closing PR #23972 and removing active labels.