Improve cache clean summary and trigger event

[TonyCTHsu]

Motivation:

From this previous run for cleaning cache: https://github.com/DataDog/dd-trace-rb/actions/runs/13317290722

I learn that:

1. The cache clean summary is not accurate with the status
2. The cache clean does not fetch all the caches associate with the branch because the trigger event is PR closed.

What does this PR do?

1. Remove status and createdAt field from the summary since they are less useful.
2. Since cache size is limited (10Gb), modify jobs what are using caches to be triggered only with PR context instead of just branch pushes.

Change log entry
None

[datadog-datadog-prod-us1]

Datadog Report

Branch report: tonycthsu/improve-cache-clean-summary
Commit report: 55c03ab
Test service: dd-trace-rb

✅ 0 Failed, 20103 Passed, 1360 Skipped, 3m 15.73s Total Time

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.69%. Comparing base (eac4961) to head (55c03ab).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4386   +/-   ##
=======================================
  Coverage   97.69%   97.69%           
=======================================
  Files        1352     1352           
  Lines       82735    82734    -1     
  Branches     4200     4200           
=======================================
+ Hits        80824    80825    +1     
+ Misses       1911     1909    -2     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-13 22:18:56

Comparing candidate commit 55c03ab in PR branch tonycthsu/improve-cache-clean-summary with baseline commit eac4961 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.