Proto/Quebec: Snapshot Quebec

This MR snapshots Quebec as Protocol 21. It:

• reverts Qena changes to QuebecA
• introduce QuebecB changes
• bumps global_limit_of_staking over baking to 9
• removes the Qena UAPO from the shell
• updates Quebec vanity hash
• updates the whole repositiory accordingly
• updates the documentation to reflect these changes

How to manually test

Quebec can be manually tested from a sandbox node:

# Build octez
make
# start a sandbox node in a terminal
./src/bin_node/octez-sandboxed-node.sh 1 --connections 0 
# in another terminal prepare the sandbox client
eval `./src/bin_client/octez-init-sandboxed-client.sh 1` 
# activate quebec
octez-activate-quebec

You should then observe the following message:

In case anyone would like to inject it, please use

octez-client submit proposals for <baker_alias> PsQuebecnLByd3JwTiGadoG4nGWi3HYiLXUjkibeFV8dCFeVMUg --force

--force is necessary if you are using an octez release built before this MR (for instance v20.1, v20.2 or v20.3).