apex: drop `java_import` support

java_import doesn't support dex jar which is necessary to be packaged in
an APEX. Supporting this would require non-trivial work. By the way
java_import is not used and there is a workaround.(defining java_library
and static-linking with it)

We drop the support for `java_import` in APEX.

Bug: 139175488
Test: m (soong tests amended)
Change-Id: I924386571079090c701276d87f665ce7fbb6f074