Prop 63: Upgrade the chain to agoric-upgrade-12

##This proposal if voted will upgrade the chain to agoric-upgrade-12
##

Release details:
- Reduce the BlockParams.MaxBytes consensus parameter to 5MB
- Enable restore from State Sync with larger payloads, which was previously broken
- Avoid a potential consensus failure when the node is restarted during busy blocks
- Allow a brand new chain to be launched with a functioning walletFactory contract (previously this only worked for chain upgrades)
- Allow usage of outbound IBC in JS smart contracts

This code has satisfied all pre-release/testnet validation checks, and is now recommended for chains to upgrade from the previous release. As a state-machine-breaking upgrade, once approved, all chain validators will need to upgrade to this new version (after the chain halts due to reaching the height required in a governance proposal).

Important note for anyone generating state-sync snapshots for use by new nodes:

In order to produce state-sync snapshots, beginning with agoric-upgrade-11 your node must have a “complete” JS database. If your DB isn’t complete, the state-sync generation process will fail. If you have been running a node continuously since the Mainnet 1B upgrade (agoric-upgrade-10), then your DB will be complete.

If you created your node from a state-sync restore before agoric-upgrade-11, or if you used a community snapshot that had itself restored from state-sync, then your DB will not be complete. You can restore from state-sync with agoric-upgrade-12 to obtain a complete DB.

#Discussion#
Discussion for this release will take place in the Agoric community forum. https://community.agoric.com/t/agoric-upgrade-12/538/1

#Release#
https://github.com/Agoric/agoric-sdk/releases/tag/agoric-upgrade-12

#Details of Upgrade Time#
The proposal targets the upgrade block to be 12586889, anticipated to be on or around 21th November 2023 at 17:00 UTC.