Rewrite the handling for the `CxxStdlib` implicit linking to use a
slightly more functional style for filtering. Additionally, add Windows
to the list providing the overlay. The Windows linking scenario is a
slightly more complicated as the library names differ between static and
dynamic variants to disambiguate between import libraries and static
libraries. Take this into account when embedding the library name so
that the linker can find the appropriate content.
Also, make some related changes, like updating a path in the Android doc, making sure the
`unknown` vendor is always used, and using `CPU` instead of `CODEGENERATOR`.
`Swift` is the name of the Swift standard library module. Creating another module with this name breaks assumptions in the compiler and caused these two tests to fail.
