Refactoring [1/3]: renames for better terminology

[nolar]

Code refactoring (part 1 of 3): terminology fixes and look-ahead alignments.

Issue : preparation for #59 #187 #142
Followed by #210 (part 2/3), #211 (part 3/3).

Description

This PR is purely for renaming the classes and methods (massive, but simple) — a part of the code refactoring needed to extend Kopf with the startup/cleanup/(re-)authentication background activities.

Adding "activities" requires some terminology corrections, specifically naming the "resource"-related causes/handlers/registries as such.

Now: they exist as the only possible form of causes/handlers/registries. Adding the activity-specialised classes/methods in addition to generic-looking but resource-specialised classes/methods will create a confusion.

Briefly:

• custom_object_handler -> resource_handler (to be paired with activity_handler).
• SimpleRegistry -> ResourceRegistry (to be paired with ActivityRegistry)
• GlobalRegistry -> OperatorRegistry (for the legacy method extraction & deprecation later).
• ..._event_watching_... -> ..._resource_watching_... (causes, handlers, registries).
• ..._state_changing_... -> ..._resource_changing_... (causes, handlers, registries).
• get_state -> get_essence (a leftover from Annotate all the code with the types #200: the "state" word is reserved for the reactor's state persistance, and should not be used for the resources' minified bodies (now: "essence")).

There are NO behavioral changes. The public interfaces are kept unmodified. These are the internal changes only.

Some of these renames were introduced in #202, and never were released yet (despite merged to master), so it is safe to rename it again without breaking the public interfaces of any Kopf version.

Types of Changes

• Refactor/improvements

[zincr]

🤖 zincr found 0 problems , 1 warning

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