[wasm] WBT fixes, and rationalization to allow improved testing (#89360)

[wasm] WBT fixes, and rationalization to allow improved testing (#89360)

* Move DotNetFileName.cs, and TestUtils.cs to Common

* Move some types from BuildTestBase.cs to separate files

- FileStat
- BuildPaths
- BlazorBuildOptions
- GlobalizationMode

* Move AssertTestMainJsAppBundleOptions.cs to Common

* Instead of globalizationMode=null use GlobalizationMode.Default

* Merge behaviors for the various project types

- Move parsing bootjson, checking icu assets, symbols to ProviderBase, so it can
  be used by all the project types. These come from WasmAppBuilder which
  is shared by all the projects.

- Instead of multiple separate ways to build the project, use one
  `BuildTestBase.BuildWithoutAssert` method that uses `DotNetCommand` to
  build. And all the project types can use this.
  - This allows having any build customizations or fixes to be in once
    place, and the outputs to be consistent.

- Instead of having `UseWebcil` in various option types, use it directly
  as needed, because this setting is *not* changed per test, rather it
  is fixed per run.

- Rationalize figuring out bin framework directories

Known limitations:
- Wasm template tests use a TestMainJs provider to assert the bundle
  because the templates are not yet based on wasm sdk.
- Blazor has a bug due to which all the icu assets get deployed
  irrespective of settings, so asserting that is disabled.
- Also, blazor does not yet support symbols file.

* Update tests to track api changes
* CI: don't trigger jobs when WasmBuild.sln changes

* Address feedback from @ilonatommy
* Address feedback from @ilonatommy - simplify icu assert code