What's Changed

Stability Improvements

Add merge_group to workflow file by @graydon in #4360
Support building core with thread sanitizer by @marta-lokhova in #4337
Rework github action caching by @graydon in #4367
Remove the bors-auto-branch short circuit from ci-build.sh by @graydon in #4370
Improve performance of dump-ledger by @MonsieurNicolas in #4361
Misc fixes to the caching logic by @graydon in #4373
Bucketlist db invariant by @SirTyson in #4369
ApplyBucketWork at per-bucket level by @ThomasBrady in #4314
Only run ci on push to real branches by @graydon in #4375
Fail loadgen when pending accounts are found in available accounts list by @bboston7 in #4372
Fixed EXPERIMENTAL_BUCKETLIST_DB_INDEX_PAGE_SIZE_EXPONENT by @SirTyson in #4378
Update overlay survey script with lessons learned during testnet run by @bboston7 in #4358

3651 prefetch entries in soroban ops by @ThomasBrady in #4178
Settings upgrades for increasing the maximum Soroban key size to 250 bytes by @dmkozh in #4371
Add initial version of the debug info gathering script by @jacekn in #4352

Full Changelog: v21.1.0...v21.2.0