aconfig: update aconfig cpp integration tests

Note a new cc_test target aconfig.test.cpp.test_mode is added instead of
reusing the old aconfig.test.cpp test target is becuase the test and
production version codegen flag lib has symbol conflict, one should only
link one at a a time.

Bug: b/291068147
Test: atest aconfig.test.cpp/aconfig.test.cpp.test_mode
Change-Id: Ifd52fd6eb7538fba90a13f0a6618a33a69b2358e