Use local variations for versionsMutator

Use local variations and an alias for the "" variation for
versionMutator.  Local variations are used here because the variation
of one module doesn't affect the variation it should depend on - a
module with variation version:29 will manually link against dependencies
with the correct version variation, and don't need it to be automatically
resolved.  The alias allows other modules to depend on a module
mutated by the version mutator without specifying the version: ""
variation.  This allows removing the variation on genrule modules.

The motiviation here is to make sure versionMutator calls AliasVariation,
which will allow the previous linkageMutator to also use AliasVariation.

Bug: 162437057
Test: no change to build.ninja, make_vars-aosp_crosshatch.mk, Android-aosp_crosshatch.mk or late-aosp_crosshatch.mk
Change-Id: Ibb030cc4334e47511b8ab5bc3eb8a5ae39ad0023