Standardize ANSI markup on all terminal output sections

[jeffwright13]

Currently (7.2.0.dev264+g6ad32a9c5), the console heading for some sections is colorized ('warnings', 'short test summary info'); while other sections are not (ERRORS, FAILURES, PASSES, and 'rerun test summary info' if the pytest-rerunfailures plugin is installed). Also, the 'test session starts' and 'short test summary info' sections are in bold, while none of the others are.

Enhancement request is to standardize ANSI markup for the various sections. If it were up to me, I would simply add colors to the section headings that are not colored: PASSES (green), FAILURES (red), ERRORS (yellow).