feat!: rewrite API

[ObserverOfTime]

Starting with the type stubs to show what the new API will look like (subject to change).
Breaking changes are marked with !.

Additions:

• LANGUAGE_VERSION
• MIN_COMPATIBLE_LANGUAGE_VERSION
• Point(row, column)
• Language.__repr__()
• Language.__eq__(): checks ptr
• Language.__int__(): returns ptr
• Language.__index__(): returns ptr
• Language.__hash__(): returns ptr
• Node.__str__(): returns the S-expression
• TreeCursor.goto_first_child_for_point(point)
• TreeCursor.__copy__(): returns copy()
• Query(language, source)
• Parser(language, included_ranges, timeout_micros)
• Parser.language (getter + setter)
• Parser.included_ranges (getter + setter)
• Parser.timeout_micros (getter + setter)
• Range.__hash__()

Deprecations:

• Node.sexp(): use str()
• Tree.text: use root_node.text
• TreeCursor.goto_first_child_for_point(row, column): use goto_first_child_for_point(point)
• LookaheadIterator.reset(language, state): use reset_state(state, language)
• Parser.set_language(language): use Parser(language) or language setter
• Parser.set_included_ranges(ranges): use included_ranges setter
• Parser.set_timeout_micros(timeout): use timeout_micros setter

Removals:

• Language(path, name) !
• Language.build_library(...) !
• Language.name !
• Language.lib
• Language.language_id: use int()

Changes:

• Language() only accepts a single integer argument. !
• TreeCursor.descendant_index is changed to a property. !
• LookaheadIterator.language returns a Language instance. !
• LookaheadIterator.reset_state(...) accepts an optional language argument.
• Query.captures(...) arguments must be keywords (except for node).
• Query.matches(...) arguments must be keywords (except for node).
• Range.__repr__() prints attributes in the same order as the Range() arguments.
• Range() arguments are no longer considered optional.

Internals:

• Drop support for Python 3.8.
• Separate the C code into multiple files.
• Use the pymalloc memory interface.
• Handle invalid inputs to prevent segfaults.
• Improve the docstrings, using core docs where possible.
• Update the tests, replacing submodules with parser packages.

[ObserverOfTime]

It's finally done! @amaanq