Add new declarative @observe which ignores 'create' events by default

[frmdstryr]

In order to avoid unnecessary calls to to _update_proxy (which by default only handles the update event type anyways), this change adds a new observe decorator in enaml.core.declarative that updates the default change_types flag to ignore create events. The widget declarations were updated to use the new import instead of the one from atom.api.

The static observer added by the declarative metaclass will also ignore created events.

Any 3rd-party code using the original atom.api for custom members will be unchanged unless it relied on a create event from a superclass member.

If someone needs the create event, either use the observe decorator from the atom.api or pass in the change_types flags for the needed. If the member had @observe on a super class, you can re-bind it with new flags to change the events triggerd.

[MatthieuDartiailh]

This looks really nice !

[MatthieuDartiailh]

The 3.7 fails are expected we are dropping support for it bit the CI update is a pending PR.

[MatthieuDartiailh]

I managed to fix the CIs though so could you rebase so that at least this is green ?

[codecov-commenter]

Codecov Report

Merging #479 (57c5121) into main (ebcfec8) will decrease coverage by 0.16%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #479      +/-   ##
==========================================
- Coverage   73.23%   73.06%   -0.17%     
==========================================
  Files         316      316              
  Lines       24123    24125       +2     
  Branches       55       55              
==========================================
- Hits        17666    17628      -38     
- Misses       6457     6497      +40     

[MatthieuDartiailh]

Actually for the docs in their current state I do not see where to add the information. It is a bit advanced for the getting started. it may have to wait for a doc overhaul...

[MatthieuDartiailh]

The coverage change is somewhat expected since we generate less event at start-up and the tests do not exert the widget beyond this point for most of them.

[MatthieuDartiailh]

@frmdstryr let me know your opinion regarding the documentation but with an entry in the release notes I believe this is good to go.

[frmdstryr]

Maybe there should be something in the Architecture Reference?

[MatthieuDartiailh]

I think so, too, but this is currently empty. If you are inspired, feel free to get the section started.