Fix BA2022 verification for long paths

[Martin Řezník (martin-reznik)]

Promotes the long-path fix for BA2022 into main. The change was staged on fix/ba2022-long-paths via #1214 and is now being promoted.

What this does

• BinSkim.Driver/app.manifest — opts the process into longPathAware so native Authenticode verification (WinVerifyTrust) can open targets whose path exceeds MAX_PATH (260).
• Test.FunctionalTests.BinSkim.Rules/RuleTests.cs — adds the BA2022_SignSecurely_LongPath_Pass regression test and disposes the analysis context per iteration in the shared test harness.
• Directory.Packages.props — bumps Microsoft.NET.Test.Sdk 17.12.0 → 17.14.1 (supports the dynamic test skip used by the new test).

Scope / known limitations

• The manifest opt-in only takes effect where the OS also has LongPathsEnabled=1 (Windows 10 1607+). It is inert otherwise — notably on Microsoft-hosted / default agents, which don't set it and can't change it at runtime.
• It does not change the diagnostic emitted when a target still can't be read: a file-access failure (CRYPT_E_FILE_ERROR) is still reported as a BA2022 "insecure signing" error rather than an analysis failure. That soundness gap is tracked separately.
• The new regression test self-skips unless LongPathsEnabled=1, so it provides no coverage on agents without that setting.

Refs

• Builds on Fix BA2022 verification for long paths #1214.
• Related to Unclear Error message when the path of the file too long #977 (partial). Intentionally does not auto-close it — the "unclear error message" / misclassification half is still open; the durable fix is managed Authenticode validation ([RULE REQUEST] Rewrite BA2022 to perform Authenticode validation without Windows-native dependencies #1058).