Rename `tezos-*` executables into `octez-*`

We recently gave a name to the implementation of Tezos in this repository: Octez.

It thus makes sense to rename all executables (tezos-node -> octez-node, tezos-client -> octez-client, tezos-codec -> octez-codec, tezos-baker-010-PtGRANAD -> octez-baker-010-PtGRANAD…).

Backward Compatibility and Deprecation Period

We will probably want to have symbolic links be produced at compile-time so that users that are used to run tezos-X can still run tezos-X. At least for a few months, with communication to tell people to update their scripts.

We can also have the node detect whether it was called from the symbolic link or not (using $0) and print a warning if it was.

Other Changes

All tezos-* libraries, and in particular the Opam packages, should also be renamed. (Don't hesitate to split this issue in two.)

In Details

• rename the binaries in the Makefile (targets build, build-sandbox, clean), but create symbolic links from the old names to the new names (e.g. ln -s octez-node tezos-node)
• update .dockerignore and .gitignore
• update GitLab CI YAML files
• update Dockerfile, the entrypoint (scripts/docker/*), and scripts/tezos-docker-manager.sh
• update static binary names
• update documentation:
  • rename everywhere
  • say that the old names are deprecated
  • this change can only be merged once this renaming is actually released though
• rename in Emacs folder
• rename in all scripts in scripts/
• rename in tests
  • Flextesa: rename in sandbox.Makefile
  • rename in Python tests
  • rename in Tezt
• rename opam packages (dune and .opam files everywhere) => may be easier with the Manifest (!3366 (merged))