Add TestOnlyProvider for test_module_config

This one is trivial as these modules are always tests and
top-level-test-targets and don't have any complicated struct composition

This requires aosp/3045317 for "m all_teams" to work for
test_module_config_host.

Test: go test ./tradefed_modules
Test: m all_teams
Change-Id: I229e7690088e996452784183a852325c3003ee93