Unify linking file composition for wasi and wasm.

[ilonatommy]

Follow up for #107253 (comment).

In browser we don't have single file mode yet, so linking projects with long paths is not a problem. However, maybe we can benefit in the future from the fix we applied to WASI. This PR moves from WASI-only to WASM-targets.

• Add a test (it was not failing without the fix, it's just to prove we are not breaking anything). It has to test native build, otherwise we don't trigger the linking response file creation (_BrowserWasmWriteRspForLinking).
• Moves relative path logic from WasiApp.targets to WasmApp.Common.targets.

ToFix:

• Browser: e.g. Wasm.Build.NativeRebuild.Tests.SimpleSourceChangeRebuildTest.SimpleStringChangeInSource, no idea what's going on
  CompareStat failed: [Expected changed file: rebuild_simple_Release.dll.o]
  = Browser, e.g. Wasm.Build.Tests.BuildPublishTests.BuildThenPublishWithAOT,

Assert.Matches() Failure: Pattern not found in value
      Regex: "build_publish_Release_\\S+.dll.bc -> build_publish"···
      Value: "[]   Determining projects to restore...\n[]   All "···

and many more

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