Add test for startSession with lsid

[chilagrow]

Description

Add test ambiguous logic for startSession creating two sessions. Unfortunately this test only runs on proxy for now.

Closes #5309.

Readiness checklist

• I added/updated unit tests (and they pass).
• I added/updated integration/compatibility tests (and they pass).
• I added/updated comments and checked rendering.
• I made spot refactorings.
• I updated user documentation.
• I ran task all, and it passed.
• I ensured that PR title is good enough for the changelog.
• (for maintainers only) I set Reviewers (@FerretDB/core), Milestone (Next), Labels, Project and project's Sprint fields.
• I marked all done items in this checklist.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 42.78%. Comparing base (cff1577) to head (4afc74e).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5333      +/-   ##
==========================================
- Coverage   42.79%   42.78%   -0.02%     
==========================================
  Files         172      172              
  Lines       18427    18427              
==========================================
- Hits         7886     7884       -2     
- Misses      10111    10113       +2     
  Partials      430      430              

see 4 files with indirect coverage changes

Flag	Coverage Δ
integration	46.04% <ø> (+<0.01%)	⬆️
mongodb	9.27% <ø> (ø)
mongodb-1	9.27% <ø> (ø)
postgresql	45.20% <ø> (-0.07%)	⬇️
postgresql-1	35.50% <ø> (-0.51%)	⬇️
postgresql-2	35.74% <ø> (+0.37%)	⬆️
postgresql-3	36.43% <ø> (-0.19%)	⬇️
postgresql-4	35.70% <ø> (+<0.01%)	⬆️
postgresql-5	35.26% <ø> (-0.02%)	⬇️
unit	13.10% <ø> (ø)
yugabytedb	42.25% <ø> (+<0.01%)	⬆️
yugabytedb-1	32.06% <ø> (-0.46%)	⬇️
yugabytedb-2	32.54% <ø> (+0.53%)	⬆️
yugabytedb-3	34.28% <ø> (+0.25%)	⬆️
yugabytedb-4	32.23% <ø> (+0.20%)	⬆️
yugabytedb-5	32.68% <ø> (+0.13%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
clientconn	57.93% <ø> (ø)
dataapi	6.61% <ø> (ø)
documentdb	15.29% <ø> (+0.07%)	⬆️
handler	76.47% <ø> (-0.15%)	⬇️

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Pull Request Overview

This PR adds a test to verify that calling startSession with an lsid parameter creates two distinct sessions in the system. The test validates the ambiguous logic behavior where both the provided lsid and a new session ID are created and stored.

• Adds TestStartSessionWithLSIDCreatesTwoSessions function to test session creation behavior
• Integrates with $listLocalSessions aggregation to verify both session IDs exist
• Uses wire protocol directly for startSession and driver for session listing

Comments suppressed due to low confidence (2)

integration/session/startsession_test.go:559

• [nitpick] The variable name containsLsidF is unclear. Consider renaming to containsLsid or lsidFound for better readability.

		containsLsidF := slices.ContainsFunc(sessionIDs, func(id wirebson.Binary) bool { return wirebson.Equal(lsid, id) })

integration/session/startsession_test.go:562

• [nitpick] The variable name containsSessionIDF is unclear. Consider renaming to containsSessionID or sessionIDFound for better readability.

		containsSessionIDF := slices.ContainsFunc(sessionIDs, func(id wirebson.Binary) bool { return wirebson.Equal(sessionID, id) })