WebKit projects are built in Xcode using header maps, so each header file needs a unique name. WebGPU project has two headers named `ShaderModule.h`. Since paths aren't used to disambiguate headers, I propose prefixing all WGSL AST node headers with `AST` and removing the nested directory structure.
<rdar://problem/101198489>
Pull request: https://github.com/WebKit/WebKit/pull/5426
Committed 255614@main (2b6ef0c64240): <https://commits.webkit.org/255614@main> Reviewed commits have been landed. Closing PR #5426 and removing active labels.