Release notes:

Protocol changes

This release is the first release that supports protocol version 13:

Made changes to the way we internally process items from connections and general work to be more fair. This avoids situations where some events would cause arbitrary delays in other parts of the system.
Fixed issues in how we ask other peers for data that we need during consensus rounds. This reduces the time it takes to propagate SCP messages.
Fixed issues in how parameters to command line catchup were inconsistently processed leading to not always exactly replaying the desired range.
Improved some edge cases for cleaning up the mempool, that would lead to certain transactions getting temporarily stuck.
Fixed issues in the simulation code used to run performance analysis.
Made catchup messages clearer.
Fixed bugs in the survey script that were causing surveys to stop too early.
Command line catchup was reporting a bogus 0 when catching up to the latest ledger.

Support for the old v1 meta format was dropped ahead of protocol 13 support. Downstream systems must now use the meta v2 format that can represent pre-post meta properly.
The metric ledger.age.closed has been changed from a Timer into a Bucket as to allow systems to perform lossless aggregation of the metric over large periods of time.