Refactor logging init flags

Rather than limiting debug log control to just debug or not, replace the
init flags with INIT_default_log_level and INIT_log_level_for_tag which
allows finer grained control of which log levels to enable.

This commit also disables some tags by default on Floss which are overly
verbose and limits the debug log level unless a verbose flag is
provided.

Bug: 274672964
Tag: #floss
Test: Load on ChromeOS and observe generated logs.

Change-Id: Iace11364ea28daf85663edae1dd21bfd16e073a8