Introduce prebuilt_vendor module type

prebuilt_vendor installs the file under `<partition>/vendor`
directory. The module is used for prebuilt_* auto generation in fsgen,
and is neverallowed so that the module cannot be used in Android.bp
files.

Test: m nothing
Bug: 381888358
Change-Id: Id5fe3f5435437da7806067be99c21c4d55a91e97