Run apexDirectlyInAnyMutator even when module is disabled

`DirectlyInAnyApex` determines the additional flags that used to
generate stubs, with different flags for platform vs apex libraries.
Run this mutator even when `enabled` is false on the implementation
library, so that the stub variant gets the right flags.

Test: With https://r.android.com/3254299, lunch
aosp_panther_hwasan-trunk_staging-userdebug & m libbase
Test: presubmits

Bug: 366047774
Change-Id: I66b396a32dd85f47698ffcdadb944de8a11c022f