The new compatibility tests are in `tests/compat`.
This includes the following:
- `old_venv` fixture which allows executing some arctic commands frow
  within a custom venv.
- 2 compatibility tests. One of which showcases an issue with modifying
  library options of old environments.
- Tweak to the Build and Test workflow to run the compat tests only on
  newer python versions

Previously modifying a library option with a new version (>=v3.0.0)
would break old libraries (<v3.0.0)

This was because of the storage overrides introduced in v3.0.0.

This change moves the logic to modify a library option to C++
and it does the protobuf modification without applying a storage
override.

This makes storage overrides work well with both old libraries (as
demonstrated by now passing compatibility tests) and with new libraries
(as confirmed by test_arctic_library_management.py)

- Exposes a `read_unaltered_lib_cfg` method for the `LibraryTool`
- Uses it in compatibility modification test to verify that we only
  change the new fields

When destructing the mongo storage it was possible to destruct the api
instance before destructing the pool.

Moved the instance from the `MongoStorage` to the `MongoClient` to be
kept as a guard around the `mongocxx::pool`. `MongoStorage` didn't need
any sensitive mongocxx objects.

We also disable mongo tests for 4.5.0 as it contains the problematic
segfault.

There have been some mono issues with ubuntu-latest, so we reverted to
ubuntu-22.04 for now.

The cibw-docker-image workflow was not updated because updating it
causes the rebuilt of the manylinux docker image which fails because of
CentOS 7 being EOL.