This PR makes the ui-mobile-base packages directly provided as source code inside @nativescript/core

• we dont publish it as aar, xcframework in @nativescript/core anymore => smaller npm package
• we dont build it while building @nativescript/core => @nativescript/core build does not need to be done on macos anymore (maybe only better for testing). Also even a macos intel can build now and does not need visionos sdk (not available on intel)
• users apps can now patch ui-mobile-base code directly
• users can debug ui-mobile-base directly with xcode and android studio in their app
• it uses symlinks in the repo => does not break anything, you can still build ui-mobile-base to ensure it builds, or use a native test app
• ui-mobile-base source code is now built with app dependencies for androidx, ... => uniformity, easy upgrade to latest SDks, java, ...
• the only "drawback" is that app compile time might be a bit slower