[7.0.3] Fix | Reenable SqlBulkCopy in least-privilege environments

[edwardneal]

Description

This PR ports #4306 to the 7.0 branch, and this contains the full description.
The automated test uses the RAII primitives, so I've also needed to include these.

Issues

Fixes #4370.
Ports #4306.

Testing

Automated tests ported from #4306, with one addition.

[Copilot]

Pull request overview

Ports the SqlBulkCopy least-privilege fix (guarding sys.all_columns metadata access via HAS_PERMS_BY_NAME) onto the 7.0 branch, along with supporting ManualTests coverage and small shared test RAII primitives.

Changes:

• Updates SqlBulkCopy initial metadata query to conditionally query sys.all_columns based on permissions.
• Adds ManualTests coverage for unprivileged SQL logins and adjusts an existing stats-based bulk copy test for the additional query.
• Introduces shared transient database-object helpers (ServerLogin, DatabaseUser, Table) and a net462-only MemberNotNullAttribute shim for nullable analysis in ManualTests.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlBulkCopy.cs	Adds HAS_PERMS_BY_NAME gating around sys.all_columns query in the initial metadata SQL batch.
src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/SqlBulkCopyTest/UnprivilegedLogin.cs	Adds ManualTests validating SqlBulkCopy behavior under a login denied access to sys.all_columns.
src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/SqlBulkCopyTest/CopyAllFromReader.cs	Updates expected connection statistics to account for the additional metadata/permission query.
src/Microsoft.Data.SqlClient/tests/ManualTests/Microsoft.Data.SqlClient.ManualTests.csproj	Includes new ManualTests source files (nullable attribute shim + new test).
src/Microsoft.Data.SqlClient/tests/ManualTests/Extensions/CodeAnalysis.netfx.cs	Adds a net462-only MemberNotNullAttribute shim for nullable flow analysis in tests.
src/Microsoft.Data.SqlClient/tests/ManualTests/DataCommon/DataTestUtility.cs	Adds helper properties/methods for server role membership and SQL-auth capability detection.
src/Microsoft.Data.SqlClient/tests/Common/Fixtures/DatabaseObjects/DatabaseObject.cs	Adds shared RAII base for transient database objects (create/drop + unique naming).
src/Microsoft.Data.SqlClient/tests/Common/Fixtures/DatabaseObjects/DatabaseUser.cs	Adds RAII wrapper for database users, including cross-database command execution.
src/Microsoft.Data.SqlClient/tests/Common/Fixtures/DatabaseObjects/ServerLogin.cs	Adds RAII wrapper for SQL logins with generated compliant passwords.
src/Microsoft.Data.SqlClient/tests/Common/Fixtures/DatabaseObjects/Table.cs	Adds RAII wrapper for transient tables used by tests.

[apoorvdeshmukh]

/azp run

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[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 67.94%. Comparing base (8c70cec) to head (bf84bb8).

Files with missing lines	Patch %	Lines
...Client/src/Microsoft/Data/SqlClient/SqlBulkCopy.cs	93.33%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (8c70cec) and HEAD (bf84bb8). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (8c70cec)	HEAD (bf84bb8)
CI-SqlClient	1	0

Additional details and impacted files

@@               Coverage Diff               @@
##           release/7.0    #4402      +/-   ##
===============================================
- Coverage        73.08%   67.94%   -5.14%     
===============================================
  Files              280      275       -5     
  Lines            43087    67052   +23965     
===============================================
+ Hits             31488    45561   +14073     
- Misses           11599    21491    +9892     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	67.94% <93.33%> (?)

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[paulmedynski]

/azp run

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