Rename requires files to standard names.

    Rename tools/pip-requires to requirements.txt and tools/test-requires
    to test-requirements.txt. These are standard files, and tools in the
    general world are growing intelligence about them.

Fixes: bug #1179008
Change-Id: I1a19f0c73ab48987e2ff0dade1a57a68b65f0a22
Merge "   Rename requires files to standard names."