Replace "apex_inherit" min_sdk_version

Replace "apex_inherit" min_sdk_version to a conditional setting. If
environment veriable KEEP_APEX_INHERIT is set, using "apex_inherit" as
the min_sdk_version, otherwise set the number to "29". For more detail
please refer
https://docs.google.com/document/d/1R2vZw0cQa-haAMgFyQ682uSq9aGBNQrzMHKIsU17-XY/edit?usp=sharing&resourcekey=0-gUbs463r9LCKs7vdP_Xkmg

Test: build APEX uses this library, and presubmit
Bug: 254634795
Change-Id: If7acfce5fb2e1cb1cc7208a8c57b1e1cd1499c11
Merged-In: Ie6984128e6b84ba73de3f4c08eca5560657c5ca2