Fix update-docs-website workflow triggers

[danbarr]

Changes the update-docs-website workflow to trigger explicitly as a reusable workflow instead of relying on the release event.

This addresses the issue of automatic PRs not being opened for Operator/CRD Helm chart releases since those are created via another workflow's GITHUB_TOKEN.

Fixes stacklok/docs-website#74

The previous attempt, #1477 failed and was reverted because the helm releaser needed secrets: inherit passed to it from its own parent (run-on-main-charts.yml), and because the chart-releaser-action output was not as expected. This revision fixes both.

Note for the helm releaser; since chart-releaser-action might process multiple Helm charts in one workflow, I had to build a JSON list of the releases to then matrix the docs update workflow call. It's ugly, but it works.

Signed-off-by: Dan Barr 6922515+danbarr@users.noreply.github.com

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.65%. Comparing base (09c2827) to head (4338e97).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1755      +/-   ##
==========================================
+ Coverage   40.61%   40.65%   +0.04%     
==========================================
  Files         184      184              
  Lines       21309    21309              
==========================================
+ Hits         8654     8663       +9     
+ Misses      12000    11994       -6     
+ Partials      655      652       -3     

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[coveralls]

coverage: 37.924% (+0.02%) from 37.903%
when pulling 4338e97 on update-docs-workflow
into 09c2827 on main.