Offer valid active-pattern imports and completion edits

[T-Gro]

Description

Suggest active-pattern imports in pattern positions and apply completion edits with the correct qualification and open placement. Do not offer unusable or duplicate imports.

Depends on #20719; targets t-gro-active-pattern-implementation. Azure PR validation now accepts t-gro-* maintainer targets so this dependent layer can run the native editor suite; push triggers and pipeline jobs are unchanged.

No closing issue.

Local validation with pinned SDK 11.0.100-rc.1.26420.103 and BUILDING_USING_DOTNET=true:

• dotnet fantomas . — passed, no changes.
• git diff --check — passed.
• dotnet test --project tests/FSharp.Compiler.Service.Tests/FSharp.Compiler.Service.Tests.fsproj -c Release --filter-class '*ActivePatternCompletionTests*' --filter-class '*AssemblyContentProviderTests*' --filter-class '*OpenDeclarationInsertionTests*' --filter-class '*CompletionPatternMatchingTests*' --report-spekt-xunit --results-directory /Users/tomasgrosup/.copilot/session-state/32e5a10e-79d0-45aa-8b49-4251a4bc61af/files/fcs-related-results /bl:/Users/tomasgrosup/.copilot/session-state/32e5a10e-79d0-45aa-8b49-4251a4bc61af/files/fcs-related.binlog — passed: 85 passed, one existing explicit skip, no failures. The same selection also passed with TEST_TRANSPARENT_COMPILER=1: 85 passed, one explicit skip, no failures.
• dotnet test --project vsintegration/tests/FSharp.Editor.Tests/FSharp.Editor.Tests.fsproj -c Release --filter-class '*ActivePatternEditorTests*' --report-spekt-xunit --results-directory /Users/tomasgrosup/.copilot/session-state/32e5a10e-79d0-45aa-8b49-4251a4bc61af/files/editor-local-results /bl:/Users/tomasgrosup/.copilot/session-state/32e5a10e-79d0-45aa-8b49-4251a4bc61af/files/editor-local.binlog — blocked at restore on macOS by NU1201: Unix test utilities target net11.0, while editor tests require net472. Native Windows execution of all 28 new scenarios and related Add Open/completion tests is pending CI.

Checklist

• Test cases added

• Performance benchmarks added in case of performance changes

• Release notes entry updated:

  Please make sure to add an entry with short succinct description of the change as well as link to this pull request to the respective release notes file, if applicable.

  Release notes files:

  • If anything under src/Compiler has been changed, please make sure to make an entry in docs/release-notes/.FSharp.Compiler.Service/<version>.md, where <version> is usually "highest" one, e.g. 42.8.200
  • If language feature was added (i.e. LanguageFeatures.fsi was changed), please add it to docs/release-notes/.Language/preview.md
  • If a change to FSharp.Core was made, please make sure to edit docs/release-notes/.FSharp.Core/<version>.md where version is "highest" one, e.g. 8.0.200.

  Information about the release notes entries format can be found in the documentation.
  Example:

  • More inlines for Result module. (PR #16106)
  • Correctly handle assembly imports with public key token of 0 length. (Issue #16359, PR #16363)
    *while! (Language suggestion #1038, PR #14238)

  If you believe that release notes are not necessary for this PR, please add NO_RELEASE_NOTES label to the pull request.