logger: add trace, count --verbose/--quiet

[casperdcl]

• count -q/-v CLI flags to determine verbosity
• add trace/TRACE logging level (more verbose than debug)
• move some (e.g. database/state cmd) debug logging to trace
• add tests
  • fix/update tests
• fixes logger: disable state logging by default #2332
• related (maybe fixes?) ui / logger: rethink verbosity #2329

[...] if you are convinced that you need custom levels, great care should be exercised when doing this, and it is possibly a very bad idea to define custom levels if you are developing a library [...] if multiple library authors all define their own custom levels [...]

-- https://docs.python.org/3/howto/logging.html#custom-levels

We already do disable_other_loggers() so muhuhu hahaha.

-- @casperdcl

# before
dvc (logging-counts)$ dvc status -v | wc -l
34
# after moving state commands to trace (`-vv`)
dvc (logging-counts)$ python -m dvc status -v | wc -l
20

[casperdcl]

this pretty much summarises this PR.

[casperdcl]

not particularly fussed about colours - feel free to suggest others

[skshetry]

We already do disable_other_loggers() so muhuhu hahaha.

We only disable loggers on cli commands.

[casperdcl]

We could still merge this and if/when a user takes issue with this we can look into work-arounds. Really using DVC API + another package which adds a logging level other than the fairly common TRACE=5 is probably very unlikely.

[pmrowla]

agree with @casperdcl, even if defining custom log levels isn't recommended for libraries, it makes sense for us to have a trace level in DVC, and it seems pretty unlikely that it will actually cause any issues in the future.