[DPE-5658] Update COS alert rules

[a-velasco]

Issue

Alert rule descriptions do not provide much guidance about what actions the user can take.

Solution

Improve the descriptions of the COS alert rule expressions.

The format should be:

1. What happened, or what is the problem
2. What can the user do to recover, or investigate further (this is the part that's usually missing)

Here is a good example:

summary: PostgresSQL SSL compression active (instance {{ $labels.instance }})
description: |
Database connections have SSL compression enabled. This may add significant jitter in replication delay.
Replicas can turn off SSL compression via `sslcompression=0` in `recovery.conf`.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.74%. Comparing base (b5711ae) to head (8fdfac6).
Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #727      +/-   ##
==========================================
+ Coverage   70.65%   71.74%   +1.08%     
==========================================
  Files          11       12       +1     
  Lines        2999     3047      +48     
  Branches      523      465      -58     
==========================================
+ Hits         2119     2186      +67     
+ Misses        767      754      -13     
+ Partials      113      107       -6     

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[marceloneppel]

LGTM! Thanks Andreia!

[lucasgameiroborges]

Nice! Thanks!

[taurus-forever]

Same question "VALUE" has been randomly removed. Can you please explain it. Tnx!

[a-velasco]

@taurus-forever Merging to keep updated with other SQL repos. Future work is planned to investigate these variables and continue improving the rules.