Move kotlin stdlib to normal dependency tag

The kotlin standard library was added with a custom dependency tag,
which then required special handling later.  We know up front whether
it will be treated the same as a static_libs or libs dependency, so
just reuse staticLibTag or libTag, and remove all the special handling.

Bug: 308016794
Test: TestKotlin
Flag: exempt REFACTOR
Change-Id: I2c5601faec284d88f28e13378d9cbffc24560efa