♻️ REFACTOR: EntityExtrasMixin -> EntityExtras

[chrisjsewell]

Part of addressing #4976 and #5465

Similar to #5442, it moves the node/group extras methods to a separate "namespace", in a back compatible manner, and is another step towards #4976 (comment): removing another 10 methods on node (i.e. #5439 + #5442 + #5445, goes from 83 -> 48)

the following deprecations are made:

    _deprecated_extras_methods = {
        'attributes': 'all',
        'get_extra': 'get',
        'get_extra_many': 'get_many',
        'set_extra': 'set',
        'set_extra_many': 'set_many',
        'reset_extras': 'reset',
        'delete_extra': 'delete',
        'delete_extra_many': 'delete_many',
        'clear_extras': 'clear',
        'extras_items': 'items',
        'extras_keys': 'keys',
    }

e.g. Node.get_extra to Node.base.extras.get

To maintain parity, this PR also makes the same change to Group extras

[chrisjsewell]

@sphuber this is now rebased

[sphuber]

This was apparently missed, but I don't think I saw the deprecation warning for this. Are those warnings working properly?

[chrisjsewell]

No, the warnings are probably not "activated" for these separate system tests. Obviously, just need to set the global variable (separate PR?)

[sphuber]

Uhm, it seems like test_daemon.py is not being run at all anymore 😅 It accidentally got removed in 5d2f153 when the RPN workchains were moved to the nightly build. I will open a PR to reinstate them

[sphuber]

Still not sure about the "not directly related to its user-facing properties" because, if anything, the extras are exactly intended to be used by users. But it is just a docstring so not that important

[sphuber]

@chrisjsewell approved this so good to be merged. Would be good if you can have a look at #5468 and #5457

[chrisjsewell]

I'm just out now, feel free to merge this with a suitable message.
Maybe look tomorrow