ST API adjustments

[FichteFoll]

The next ST build will include the following changes. I'm just listing those that are relevant for us for now.

• Settings objects can be accessed like a dict natively.
• Functions to iterate and find syntax definitions.
• New enum for completion item kind.

[Thom1729]

I went through the current API docs to produce a hopefully-complete list.

Python 3.8

Compat/types

• Remove enum, pathlib, and typing from _compat and import the native versions instead.
• Simplify/update some type annotations. Possibly use from __future__ import annotations.

Other

• Make SettingsDict.update's other argument positional-only.

Sublime 4 API

Flags

New values for existing enums

• PopupOption: KEEP_ON_SELECTION_MODIFIED, HIDE_ON_CHARACTER_EVENT.
• OpenFileOption: ADD_TO_SELECTION, REPLACE_MRU, SEMI_TRANSIENT
• CompletionOptions: DYNAMIC_COMPLETIONS, INHIBIT_REORDER
• QuickPanelOption: WANT_EVENT

New enums

• CompletionFormat: TEXT, SNIPPET, COMMAND
• KindId: AMBIGUOUS, KEYWORD, TYPE, FUNCTION, NAMESPACE, NAVIGATION, MARKUP, VARIABLE, SNIPPET, COLOR_*
• Maybe one for the preconstructed kind tuples as well.
• SymbolSource: ANY, INDEX, OPEN_FILES
• SymbolType: ANY, DEFINITION, REFERENCE

Syntax

• Reimplement list_syntaxes and get_syntax_for_scope using sublime.list_syntaxes and sublime.find_syntax_by_scope.
• Return sublime.Syntax instead of SyntaxInfo namedtuple.

Settings

• Implement methods requiring iterability. (Could there be performance concerns here?)

Panels

• Reimplement Panel.exists() using View.element()?????

show_selection_panel

• Handle QuickPanelItem arguments.
• Add placeholder argument.
• Handle WANT_EVENT (i.e. make sure we pass the correct number of arguments in either case).

Ecosystem

• Create a dependency for Sublime type stubs and use it rather than bundling stubs here.
• Update UnitTesting if needed.

[FichteFoll]

Feel free to edit my initial post with these and track them there.