feat(ffi): Expose SqliteStoreBuilder::key in the FFI layer

[jmartinesp]

This allows clients to provide a raw key instead of a passphrase for the key used to encrypt and decrypt data in the store DBs.

Using a raw key with enough entropy should be safe, and we can skip the key derivation performed in the passphrase, which slows down session restoration (it's now 50% faster in my local tests).

• I've documented the public API Changes in the appropriate CHANGELOG.md files.
• This PR was made with the help of AI.

Signed-off-by:

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.95%. Comparing base (56de50c) to head (d302f5f).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6581      +/-   ##
==========================================
+ Coverage   89.93%   89.95%   +0.02%     
==========================================
  Files         382      382              
  Lines      107797   107797              
  Branches   107797   107797              
==========================================
+ Hits        96943    96967      +24     
+ Misses       7174     7161      -13     
+ Partials     3680     3669      -11     

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[codspeed-hq]

Merging this PR will not alter performance

✅ 50 untouched benchmarks

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_{Comparing feat/ffi-expose-sqlite-store-builder-key (d302f5f) with main (b6d0f8a)}

[jmartinesp]

Sorry, force pushed to fix a typo in the changelog file, there weren't any other changes in the rebase.