Feature Request - Add Dawn dependency for WebGPU rhi

[guillaume-haerinck]

Is your feature request related to a problem? Please describe.

We want to be able to use Dawn to test atom on WebGPU RHI without the need of a web-browser. Currently we have to build it manually, adding that as a third-party would allow to quickstart contributors to help on the WebGPU support of Atom.

Related to :

• Feature Request - Allow to export project to WebAssembly and run Atom on WebGPU o3de#19082

Describe the solution you'd like

Building dawn as we currently do for crashpad

Describe alternatives you've considered
None