sqlite: keep database alive while a session is open

[3zrv]

fixes: #63796

Verification

• Repro crashes (SIGSEGV, exit 139) before the change; throws ERR_INVALID_STATE after.
• New regression test fails (segfault) on an unfixed build and passes on the fixed build.
• Full test/parallel/test-sqlite-session.js suite passes (26/26).

[nodejs-github-bot]

Review requested:

• @nodejs/sqlite

[louwers]

I think a session is supposed to keep the database alive...

[3zrv]

@louwers totally right, the bug was that the session held the database with a weak ref, so it could get GC'd out from under a live session -> dangling pointer -> crash. sqlite requires sessions to be deleted before the connection closes, so a live session with a dead DB is never valid

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.14%. Comparing base (34c28d5) to head (f6b4960).
⚠️ Report is 25 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_sqlite.cc	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63797      +/-   ##
==========================================
- Coverage   90.23%   90.14%   -0.10%     
==========================================
  Files         739      741       +2     
  Lines      241639   241978     +339     
  Branches    45547    45538       -9     
==========================================
+ Hits       218031   218119      +88     
- Misses      15152    15374     +222     
- Partials     8456     8485      +29     

Files with missing lines	Coverage Δ
src/node_sqlite.h	80.64% <ø> (ø)
src/node_sqlite.cc	80.65% <25.00%> (-0.06%)	⬇️

... and 68 files with indirect coverage changes

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