Second attempt of #33242

Fixes #29953
Contributes towards #31844

Changes

• Use RestoreUseStaticGraphEvaluation which improves no-op restore by 10-15x down to 10-20 seconds.
• .builds msbuild files renamed to .proj as RestoreUseStaticGraphEvaluation throws for non .proj files without an env var set.
• Introducing subsets for libraries and mono and replacing -buildtests switch which was only working for libraries in favor of the subset switch -subset tests which works consistently.
• Fixing the Microsoft.DotNet.CodeAnalysis analyzer which wasn't running and adding missing exclusions.
• Separating restore and build phases in different parts in the repo (ie for installer.tasks) as generated props and targets need to be imported which requires a reevaluation in the build phase.
• Fix eng/docker/build-docker-sdk.ps1 by using the official build entrypoints (cc @alnikola)
• Remove a few depprojs in favor of project restore (faster restore :))
• Fix root code coverage measurement not working correctly
• Traversal support instead of dir.traversal.targets or manual build target defines.
• Introduce a root Build.proj entrypoint which is responsible for building and restoring the repository. This is necessary to enable the new NuGet fast restore which works best and fastest with a single entrypoint.
• Avoid binclashes in libraries and between libraries and installer (netstandard.depproj vs netstandard.csproj)
• Upgrading the SDK to 5.0 latest
• Code cleanup

Perf

In most cases I see improvements in the overall restore but based on it hitting the network the numbers vary slightly accross builds. That said, this should provide confidence that the regression introduced in the previous attempt is now addressed.

Thoughts on the numbers:

• Overall restore is either on parity or faster. This is because of a) a single entrypoint to restore and b) fast restore mode enabled.
• No-op/Incremental restore is MUCH faster. Incremental restore takes up to 90% less time with NuGet Fast Restore Feature.
• Libraries Test Builds should be noticeably faster in CI as it just restores what it needs.

Compared https://dev.azure.com/dnceng/public/_build/results?buildId=582003 with https://dev.azure.com/dnceng/public/_build/results?buildId=583335 and looked into other builds as well to make sure that the before numbers aren't a best or worst case.

cc @jeffkl @ericstj