feat(sqlite): SqliteStateStore has 1 write connection

[Hywan]

This patch introduces a write-only connection in SqliteStateStore à la SqliteEventCacheStore (see #5382 to learn more). The idea is to get many read-only connections, and a single write-only connections behind a lock, so that there is a single writer at a time.

This patch renames the acquire method to read, and it introduces a new write connection.

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• Address https://github.com/element-hq/customer-success/issues/591
• May fix SQLite stores sporadically fail with database is locked errors #5362

[codecov]

Codecov Report

❌ Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.42%. Comparing base (67d8db3) to head (da7a4e6).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
crates/matrix-sdk-sqlite/src/state_store.rs	89.47%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5744      +/-   ##
==========================================
- Coverage   88.42%   88.42%   -0.01%     
==========================================
  Files         360      360              
  Lines       99545    99557      +12     
  Branches    99545    99557      +12     
==========================================
+ Hits        88022    88030       +8     
- Misses       7394     7399       +5     
+ Partials     4129     4128       -1     

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[codspeed-hq]

CodSpeed Performance Report

Merging #5744 will not alter performance

_{Comparing Hywan:fix-sqlite-state-store-write-connection (da7a4e6) with main (67d8db3)}

Summary

✅ 50 untouched

[poljar]

Looks good.