Testsuite - Add special log levels: COMMAND and PASS

These new levels are meant to be used only for run_command and
subtest/subpass to highlight them from current INFO and DEBUG
messages.
New log_command and log_pass are used for that, and new options
testsuite_color_command and testsuite_color_pass are also available.
Note that the new "levels" are special cases, but they share the same
underlying level (ie its number) than INFO.

Bug 10787

Co-authored-by: Albert Gil <albert.gil@schedmd.com>