[Enhancement] <UseMauiBuild>

## Summary
Separate out the MSBuild infrastructure for MAUI from from including the package dependencies. Included in the is the ability to have a Platforms directory where Android, IOS, MacCatalyst and Windows subdirectories are automatically included or excluded based on . This build capability is extremely helpful in building non-MAUI dependent platform libraries. For example, I have a networking project that supports Android, IOS, MacCatalyst, Windows, Linux and MacOS. The project includes both platform specific and shared implementations of networking APIs.

Also, having the ability to use the build system to build non-MAUI projects on Linux cloud pipeline hosts.

## API Changes
Move the MAUI build project code into a separate package and true to include the MAUI build tools separate from the MAUI platform dependencies.

## Intended Use Case
To use the MAUI build system for projects that include platform dependencies but don’t require the MAUI dependencies. This would also enable the building of projects on Linux as it would not require the MAUI workload to be installed.

No files or tests are named. Start by locating the existing UseMaui MSBuild infrastructure and how it brings in MAUI platform dependencies; done means a separate UseMauiBuild option enables the build tools without those dependencies and supports the described non-MAUI projects on Linux.

Written by the indexing model from the issue text.