[dawn] add new port

[clemenswasser]

Fixes #35606

This is not finished and missing a lot of things!
Due to dawn depending on SPIRV-Tools internals, I wanted to ask what would be the best way forward?
Compiling SPIRV-Tools as part of the dawn port seems less than ideal, any suggestions?
I also currently get the following linker error when building (tried to force SPIRV-Tools to be built as static, but this doesn't help):
SPIRV-Tools-shared.lib(SPIRV-Tools-shared.dll) : error LNK2005: spvContextDestroy already defined in SPIRV-Tools.lib(table.cpp.obj)
Also about missing tint symbols, which I fixed by adding the library as a dependency. Seems like dawn is rarely built as a shared lib?

• Changes comply with the maintainer guide.
• The name of the port matches an existing name for this component on https://repology.org/ if possible, and/or is strongly associated with that component on search engines.
• Optional dependencies are resolved in exactly one way. For example, if the component is built with CMake, all find_package calls are REQUIRED, are satisfied by vcpkg.json's declared dependencies, or disabled with CMAKE_DISABLE_FIND_PACKAGE_Xxx.
• The versioning scheme in vcpkg.json matches what upstream says.
• The license declaration in vcpkg.json matches what upstream says.
• The installed as the "copyright" file matches what upstream says.
• The source code of the component installed comes from an authoritative source.
• The generated "usage text" is accurate. See adding-usage for context.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Only one version is in the new port's versions file.
• Only one version is added to each modified port's versions file.

[dg0yt]

Dawn and tint are optionally built as part of port skia. So this task includes deventoring it from skia's gn build. This is already done for some other skia deps.