[stable10] Sync code for 'add events for user preference changes' 31266 and 31307

[phil-davis]

Description

PR #31266 "Add events for user preference changes" happened in stable10
PR #31307 was the forward-port to master
But these had some lines different (formatting and PHPdoc...)

This PR syncs the code in stable10 to match the "good stuff" in master

(see PR #34819 for code going the other way)

Between the 2 PRs, this gets the code in sync.

Motivation and Context

Make code the same in stable10 and master

How Has This Been Tested?

CI

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:

[codecov]

Codecov Report

Merging #34820 into stable10 will not change coverage.
The diff coverage is 100%.

@@             Coverage Diff             @@
##             stable10   #34820   +/-   ##
===========================================
  Coverage       64.23%   64.23%           
  Complexity      19895    19895           
===========================================
  Files            1277     1277           
  Lines           76243    76243           
  Branches         1292     1292           
===========================================
  Hits            48971    48971           
  Misses          26893    26893           
  Partials          379      379

Flag	Coverage Δ	Complexity Δ
#javascript	53.2% <ø> (ø)	0 <ø> (ø)	⬇️
#phpunit	65.39% <100%> (ø)	19895 <0> (ø)	⬇️

Impacted Files	Coverage Δ	Complexity Δ
lib/private/AllConfig.php	94.52% <100%> (ø)	43 <0> (ø)	⬇️

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[individual-it]

only formatting changes