Compatibilize code with google3

Google3 is more strict than android codebase, and flicker had some warnings that were considered errors there (using outside context `it`, class with only companion methods, misuse of removePrefix function). Fix them for compatibility

Bug: 262241371
Test: atest FlickerLibTest
Change-Id: Idef319e836bcc9b7d395758bb3cc298ea8b8615e
11 files changed