ref(alerts): fetch group_to_groupevent once per delayed processing task

[cathteng]

Because we fetch group_to_groupevent for every rule that we need to fire groups for, this quickly takes up space in the span tree when we are trying to debug why fire_rules is taking so long. Fetching it once should also improve performance a little.

Rules can also fire for the same groups so this reduces some redundancy.

[kcons]

We should make it easier to understand what this situation means.
group_id_to_group is derived from rules_to_fire, but I think the subset of groups from rulegroup_to_event_data that were in rules_to_fire and we were able to find in the DB.
group_ids is just the raw group ids from rules_to_fire. rules_to_fire groups are themselves a subset of the groups present in rulegroup_to_event_data (i think).
So, my read is that not finding the group suggests something went wrong in fetching, which seems unexpected and probably worth escalating beyond logs.

If that's wrong, I think a comment clarifying what someone who sees this log message should be thinking is worthwhile.

[cathteng]

i can logger.error here, it will throw a sentry error

[codecov]

Codecov Report

Attention: Patch coverage is 63.63636% with 4 lines in your changes missing coverage. Please review.

⚠️ Parser warning

The parser emitted a warning. Please review your JUnit XML file:

Warning while parsing testcase attributes: Limit of string is 1000 chars, for name, we got 2083 at 1:156898 in /home/runner/work/sentry/sentry/.artifacts/pytest.junit.xml

Files with missing lines	Patch %	Lines
src/sentry/rules/processing/delayed_processing.py	63.63%	4 Missing ⚠️

Additional details and impacted files

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- Coverage   82.60%   82.60%   -0.01%     
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  Branches    22574    22574              
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- Hits       484580   484579       -1     
- Misses     100821   100828       +7     
  Partials     1232     1232