[7.0.3 Cherry-pick] AE tests: create ConversionTests keys once per class to slow error 3807 identifier exhaustion

[github-actions]

Description

Backports #4478 to release/7.0 for the 7.0.3 servicing release. The cherry-pick conflicts have been resolved manually.

This fixes recurring SQL Server error 3807 (Create failed because all available identifiers have been exhausted.) in the Always Encrypted manual tests. ConversionTests previously created a Column Master Key and Column Encryption Key for every test case, advancing SQL Server's monotonic per-database identifier counter even after the keys were dropped.

The change adds an IClassFixture that creates the keys once per test class and drops them when the fixture is disposed. Per-test tables continue to be created and dropped for each case. This substantially reduces key identifier consumption without changing the public API.

Issues

Backport of #4478.

Testing

• Source change validated by sqlclient-ci-kerberos run 20260727.4.
• Cherry-pick conflicts resolved against release/7.0; resulting branch contains the expected two-file change.

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[Copilot]

Pull request overview

Backport of the upstream fix to reduce SQL Server error 3807 (“identifier exhaustion”) in Always Encrypted manual tests by creating the CMK/CEK once per ConversionTests class instead of once per test case.

Changes:

• Added ConversionTestFixture (IClassFixture) that creates a shared CMK+CEK once per test class and drops them on fixture disposal.
• Refactored ConversionTests to consume the shared CEK from the fixture and to only drop per-test tables in Dispose().

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Microsoft.Data.SqlClient/tests/ManualTests/AlwaysEncrypted/TestFixtures/ConversionTestFixture.cs	New class fixture that creates/drops shared CMK/CEK for ConversionTests.
src/Microsoft.Data.SqlClient/tests/ManualTests/AlwaysEncrypted/ConversionTests.cs	Switches from per-test constructor key creation to using the shared fixture CEK; keeps per-test table lifecycle.

[paulmedynski]

/azp run

[azure-pipelines]

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1 pipeline(s) were filtered out due to trigger conditions.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.72%. Comparing base (e47f4f0) to head (e87af5a).
⚠️ Report is 1 commits behind head on release/7.0.

❗ There is a different number of reports uploaded between BASE (e47f4f0) and HEAD (e87af5a). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (e47f4f0)	HEAD (e87af5a)
CI-SqlClient	1	0

Additional details and impacted files

@@               Coverage Diff               @@
##           release/7.0    #4485      +/-   ##
===============================================
- Coverage        74.68%   65.72%   -8.96%     
===============================================
  Files              280      275       -5     
  Lines            43923    65953   +22030     
===============================================
+ Hits             32802    43349   +10547     
- Misses           11121    22604   +11483     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	65.72% <ø> (?)

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