Use .runner_config instead of .config

CTS TF started to read subdir .config file converted from AT.xml in the new suite impl.
This conflicts with our runner config's file extension.

Test: run vts-selftest
Bug: 78287777
Change-Id: Id234dcb11ce31c92ab841081ca5d9ee6686bc2c2
Merged-In: Id234dcb11ce31c92ab841081ca5d9ee6686bc2c2
18 files changed