meta: force compaction when there's too many slices in one chunk

[SandyXSD]

fix #4536

Known limits for value:

• MySQL: 64 KiB
• FoundationDB: 100 KB
• etcd: 1MiB

[codecov]

Codecov Report

Attention: Patch coverage is 88.31169% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 55.59%. Comparing base (46090dd) to head (808c428).
Report is 3 commits behind head on main.

Files	Patch %	Lines
pkg/meta/redis.go	76.00%	4 Missing and 2 partials ⚠️
pkg/meta/sql.go	88.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4573      +/-   ##
==========================================
- Coverage   55.66%   55.59%   -0.08%     
==========================================
  Files         158      158              
  Lines       43067    43101      +34     
==========================================
- Hits        23973    23961      -12     
- Misses      16430    16468      +38     
- Partials     2664     2672       +8     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[davies]

we can add a unit test to write 10000 times

[SandyXSD]

The etcd is misconfigured in the CI, leading to test failure whenever it runs longer than 1 minute (caused by AutoSyncInterval: time.Minute).