Improve syntax highlighting for python-ts-mode

Improve syntax highlighting for python-ts-mode

Fix fontification of strings inside of f-strings interpolation, e.g. for
f"beg {'nested'}" - 'nested' was not fontified as string.  Do not
override the face of builtin functions (all, bytes etc.) with the
function call face.  Add missing assignment expressions (:= *=).
Fontify built-ins (dict,list,etc.) as types when they are used in type
hints.  Highlight union types (type1|type2).  Highlight base class names
in the class definition.  Fontify class patterns in case statements.
Highlight the second argument as a type in isinstance/issubclass call.
Highlight dotted decorator names.

* lisp/progmodes/python.el (python--treesit-keywords): Add compound
keyword "is not".
(python--treesit-builtin-types): New variable that stores all python
built-in types.
(python--treesit-type-regex): New variable.  Regex matches if text is
either built-in type or text starts with capital letter.
(python--treesit-builtins): Extract built-in types to other variable.
(python--treesit-fontify-string): fix f-string interpolation.  Enable
interpolation highlighting only if string-interpolation is presented
on the enabled levels of treesit-font-lock-feature-list.
(python--treesit-fontify-string-interpolation): Remove function.
(python--treesit-fontify-union-types): Fontify nested union types.
(python--treesit-fontify-union-types-strict): Fontify nested union
types, only if type identifier matches against
python--treesit-type-regex.
(python--treesit-fontify-dotted-decorator): Fontify all parts of
dotted decorator name.
(python--treesit-settings): Change/add rules.  (Bug#67061)

* test/lisp/progmodes/python-tests.el
(python-ts-tests-with-temp-buffer): Function for setting up test
buffer.
(python-ts-mode-compound-keywords-face)
(python-ts-mode-named-assignement-face-1)
(python-ts-mode-assignement-face-2)
(python-ts-mode-nested-types-face-1)
(python-ts-mode-union-types-face-1)
(python-ts-mode-union-types-face-2)
(python-ts-mode-types-face-1)
(python-ts-mode-types-face-2)
(python-ts-mode-types-face-3)
(python-ts-mode-isinstance-type-face-1)
(python-ts-mode-isinstance-type-face-2)
(python-ts-mode-isinstance-type-face-3)
(python-ts-mode-superclass-type-face)
(python-ts-mode-class-patterns-face)
(python-ts-mode-dotted-decorator-face-1)
(python-ts-mode-dotted-decorator-face-2)
(python-ts-mode-builtin-call-face)
(python-ts-mode-interpolation-nested-string)
(python-ts-mode-disabled-string-interpolation)
(python-ts-mode-interpolation-doc-string): Add tests.