[Helix] Shared framework support + Templates tests (#19177)

.azure/pipelines/ci.yml

.azure/pipelines/quarantined-tests.yml

eng/helix/content/InstallAppRuntime.ps1

eng/helix/content/InstallNode.ps1

eng/helix/content/installappruntime.sh

eng/helix/content/runtests.cmd

eng/helix/content/runtests.sh

eng/targets/Helix.props

eng/targets/Helix.targets

src/ProjectTemplates/test/BlazorServerTemplateTest.cs

src/ProjectTemplates/test/ByteOrderMarkTest.cs

src/ProjectTemplates/test/EmptyWebTemplateTest.cs

src/ProjectTemplates/test/GrpcTemplateTest.cs

src/ProjectTemplates/test/Helpers/ProcessEx.cs

src/ProjectTemplates/test/Helpers/Project.cs

src/ProjectTemplates/test/Helpers/ProjectFactoryFixture.cs

...ProjectTemplates/test/Helpers/TemplatePackageInstaller.cs

src/ProjectTemplates/test/IdentityUIPackageTest.cs

src/ProjectTemplates/test/MvcTemplateTest.cs

src/ProjectTemplates/test/ProjectTemplates.Tests.csproj