Tatsu

* [exceptions] generators in exceptions break multiprocessing
* [buffering] optimize use of regular expressions

This release adds fixes, enhancements, optimizations, and documentation to the `asjson()` protocol that is used to view ASTs and models.

The bump in the minor version number because the changes to `asjson()` will likely break code that relies on the `__json__()` protocol and thus create a backwards incompatibility.

* [codegen] pass whitespace setting to parser
| * [codegen] restore default Buffer class

Fix errors in the move to `pyproject.toml`

* validate with Python 3.12 (313)
* drop support for Python 3.10 (313)
* move build configuration to `pyproject.toml` (316 317)
* evaluate constant to a Python literal when possible (304 320)
* fix `comments_re` and `eol_comments_re` so they effectively can be `None` (307 312 314)
* skip over whitespace and comments before memoizing (305 306 309 318)
* verify that `()` parses to `None` or is ignored (308)

This release makes TatSu compatible with Python >= 3.8, but still states that the compatible version is Python >= 3.10.