Release notes:

Stability improvements

• Work shouldn't be scheduled once WorkScheduler is done - fixes a potential crash on shutdown
• Add CONFIGURE_FLAGS argument to Dockerfile.testing to give better control when building ad-hoc containers
• Bring db-schema.md up to date
• Record and check TxMeta produced by tests. Strengthen testing.
• Create multi-operation transactions in LoadGen . Allows to better simulate network patterns in large scale simulations.
• Remove a confusing error message in sendMessage
• replace use of "assert" by releaseAssert*. Hardening regardless of build flags.
• Improve invariance in Herder. Simplifies herder state machine in preparation for more changes.
• ApplyLedgerWork fails correctly
• Remove unnecessary protocol checks. Consolidates protocol 14 and 15 to avoid confusion.
• Add test for op source acc to claim sponsored non native balance
• Resize ccache in ci-build.sh. CI improvement
• reduce memory usage of asan in ci. CI improvement.

New features

None

Breaking changes

None