Update the default branch to release/6.2

Update default branches for ds2 and swift-win32

Use default branch name for swift-experimental-string-processing.

This updates the packaging steps following
swiftlang/swift-installer-scripts#413

This cherry-picks the following PRs:
* GHA: shuffle the Foundation headers #918
* GHA: shuffle more files for Dispatch, Foundation #935
* Create directory before moving items #936
* GHA: adjust the installer build phases #937
* GHA: enable _Builtin_float on android #942
* Installer: Properly include Android platform #944
* Update Android root folder #943
* Packaging: Set productArchitecture #941
* Android: Update Android platform packaging #940

Co-authored-by: Saleem Abdulrasool <abdulras@thebrowser.company>

SourceKit-LSP gained a new dependency on ASN1, update the workflow to
accommodate that in the CMake invocation.

* mimalloc: Remove workaround for mimalloc

This is no longer required with mimalloc 3.0.3.

* Move mimalloc to 3.3

---------

Co-authored-by: Fabrice de Gans <fabrice@thebrowser.company>

Cherry-picked from #955

This matches upstream `build.ps1` behavior.

Cherry-picked from #954

Prepare to build swift-build in the toolchain build as it is about to
the packaged up into the installer.

Co-authored-by: Saleem Abdulrasool <compnerd@compnerd.org>

This is a cherry-pick of #943

Branch swift-build from the proper branch for `release/6.2`.