gn2bp: mark java targets as java_group

According to the docs, java target names are (somewhat) guaranteed to end in
_java. There are some other variations that are allowlisted, though it
is currently unclear if those need to be supported for our purposes.

Test: //net:net
Change-Id: I0647dac6a078790e23509d437628aed0d8d62f77
2 files changed