Fix MAX_PATH issue in SiteExtensions and move them to main build (#7177)

.azure/pipelines/ci.yml

.azure/pipelines/site-extensions.yml

build/repo.props

eng/Dependencies.props

eng/ProjectReferences.props

eng/Versions.props

src/SiteExtensions/LoggingAggregate/Directory.Build.props

src/SiteExtensions/LoggingAggregate/Directory.Build.targets

src/SiteExtensions/LoggingAggregate/SiteExtensions.sln

src/SiteExtensions/LoggingAggregate/build.cmd

src/SiteExtensions/LoggingAggregate/build/dependencies.props

src/SiteExtensions/LoggingAggregate/build/repo.props

src/SiteExtensions/LoggingAggregate/build/sources.props

...icrosoft.AspNetCore.AzureAppServices.SiteExtension.csproj

...etCore.AzureAppServices.SiteExtension/applicationHost.xdt

...xtensions/tests/Microsoft.Web.Xdt.Extensions.Tests.csproj

src/SiteExtensions/Sdk/SiteExtension.targets