[7.1.2 Cherry-pick] Add XML documentation validation to OneBranch builds and fix docs issues

[github-actions]

Description

Backports the remaining changes from #4730 to release/7.1 for 7.1.2. Most XML documentation validation infrastructure was already backported in #4752; this PR contains only the additional validator hardening, regression tests, and documentation correction.

• Reject malformed documentation IDs: empty generic arguments, unbalanced or invalid array suffixes, unmatched/nested/repeated parameter lists, parameter lists on unsupported member kinds, and empty parameters.
• Preserve valid generic, array, method, indexed-property, and conversion-operator references with regression coverage.
• Correct the SqlRowUpdatingEventArgs reference to DbDataAdapter.Update(DataSet) from an event (E:) to a method (M:).

Issues

• Source change: Add XML documentation validation to OneBranch builds and fix docs issues #4730.
• Earlier release-branch backport: [7.1] Add XML documentation validation to OneBranch builds and fix docs issues #4752.
• No additional issue closure is requested.

Testing

• sqlclient-non-official-github: Run 26280.2

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[Copilot]

Copilot review overview

🟡 Changes recommended

The array validation rejects valid dimensions whose lower bound is omitted but size is specified.

Review effort: Balanced
Findings: 1

Open (1)

• Regex rejects dimensions with omitted lower bounds · New

What changed in this PR

Backports XML documentation validator hardening and corrects an invalid method reference.

Changes:

• Validates malformed generic, array, and parameter syntax.
• Adds regression coverage for valid and invalid DocIDs.
• Corrects the DbDataAdapter.Update(DataSet) cref prefix.

File	Description
validate-xml-docs.ps1	Strengthens DocID validation.
validate-xml-docs.Tests.ps1	Adds validator regression tests.
SqlRowUpdatingEventArgs.xml	Corrects an event prefix to a method prefix.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.36%. Comparing base (ab3d40a) to head (bf2175b).
⚠️ Report is 1 commits behind head on release/7.1.

Additional details and impacted files

@@               Coverage Diff               @@
##           release/7.1    #4800      +/-   ##
===============================================
- Coverage        66.52%   64.36%   -2.16%     
===============================================
  Files              291      285       -6     
  Lines            45101    68065   +22964     
===============================================
+ Hits             30002    43813   +13811     
- Misses           15099    24252    +9153     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	64.36% <ø> (?)

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