* Rename CookieMetricsMiddleware to CookingMonitoringMiddleware
This fixes a misuse of New Relic terminology. Here we are in fact using
custom attributes; custom metrics are a different thing that we may start
using in the future.
* Rename metric -> attribute in courseware New Relic code
* Fix my weird typo
* Replace `s/metric/attribute/g` in waffle_utils and in caller
This changes:
- `WAFFLE_FLAG_CUSTOM_METRICS`
- `WaffleFlagNamespace._set_waffle_flag_metric`
- `_get_waffle_flag_custom_metrics_set` and some other unreferenced
internals
* Avoid direct use of newrelic (while we're in there)
* Fix existing typo in line I touched
* A few other "metric" names in files touched in previous renaming PRs
* Make dependency constraint note terse, and add description
ec65018306