feat(grouping): Collect grouphash metadata metrics

[lobsterkatie]

This adds a number of metrics to track grouphash metadata:

• grouping.grouphashmetadata.event_hash_basis - tracks the overall grouping method, including whether or not a hybrid fingerprint was involved

• grouping.grouphashmetadata.event_hashing_metadata.{hash_basis} - for stacktrace, message, fingerprint, security report, and fallback hashing, tracks certain hashing-method-specific data (see METRICS_TAGS_BY_HASH_BASIS for a list of what's collected)

• grouping.grouphashmetadata.create_or_update_grouphash_metadata - times the process of collecting grouphash metadata

• grouping.grouphashmetadata.backfill_needed - tracks instances in which we'd backfill missing metadata, to help estimate the load that will create. As the accompanying comment says, this greatly overestimates the number of backfills we'd actually do (since we see the same grouphashes repeatedly, and each would only need to be backfilled once), but given that all we need is an upper bound in order to set our initial backfill sample rate, it's good enough for now.

To test the first two metrics, they and their tag values have been added to the grouphash metadata snapshots. (The timer metric wasn't included because there's not much to test there, and the backfill metric wasn't included because it's temporary.)

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 96.15385% with 1 line in your changes missing coverage. Please review.

:white_check_mark: All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/sentry/grouping/ingest/grouphash_metadata.py	94.73%	0 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #81070 +/- ## ========================================== - Coverage 78.49% 78.48% -0.01% ========================================== Files 7215 7215 Lines 319793 319816 +23 Branches 44034 44040 +6 ========================================== + Hits 251009 251018 +9 - Misses 62399 62406 +7 - Partials 6385 6392 +7 ```