* Bump sdk used for testing to 6.0.100-rc.1.21402.6

* InstallWorkloadFromArtifacts: Add OnlyUpdateManifests parameter

* [wasm] Run Wasm.Build.Tests with sdk/no-workload/+EMSDK

Currently, Wasm.Build.Tests are run in two modes:

1. sdk(`$(SdkVersionForWorkloadTesting)`)+workload installed
2. sdk(from global.json)+EMSDK+LocalBuild targets

this commit changes (2) to:

2. sdk(`$(SdkVersionForWorkloadTesting)`), no workload installed, +
   EMSDK+LocalBuild targets

This makes it closer to what a user would actually use.

Also, for the workload tests, this removes `$(WasmNativeWorkload)`
always being set to `true`. The workload should be setting that, and not
the tests.

* Wasm.Build.Tests: Add test for net5.0 blazor projects

* Disable unrelated builds for now

* Revert "Disable unrelated builds for now"

This reverts commit 6fa0efe2ffcfdbcfaba3bdf519a7717809c22672.

* Rename OnlyWasmBuildTests -> TestWasmBuildTests