refactor: clean up logging

[jennifer-richards]

This brings in the logging changes made on feat/helm and feat/k8s and adjusts the log setup to be compatible with current production.

Strips out the UTILS_LOGGER_LEVEL mechanism that we're not currently using (explanation in the commit description).

Rather than bringing back the direct calls to syslog.syslog in the ietf.utils.log module, this keeps @rjsparks's change directing those logs to the datatracker logger. That logger is configured to go to syslog via the SysLogHandler.

A change on the k8s settings_local.py we deploy will be needed to do this:

LOGGING["loggers"]["django"]["handlers"] = ["console", "mail_admins"]
LOGGING["loggers"]["django.security"]["handlers"] = ["console"]
LOGGING["loggers"]["datatracker"]["handlers"] = ["console"]

which should preserve its current configuration.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.89%. Comparing base (187c2c5) to head (1e23fdc).
Report is 119 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7419      +/-   ##
==========================================
- Coverage   88.98%   88.89%   -0.09%     
==========================================
  Files         291      291              
  Lines       40717    41044     +327     
==========================================
+ Hits        36233    36488     +255     
- Misses       4484     4556      +72     

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