In IDLE colorizer, replace re with tokenizer

The current IDLE colorizer was designed when the python grammar was restricted to a context-free subtype. Parsing with RE's was sufficient or closely so to pick out substrings to be color tagged. The current grammar's sometime context-dependence make this more difficult or even impossible.

A few versions ago, the new C tokenizer used to compile Python code was exposed as a function in the tokenizer module. It replaced a python-coded tokenizer that did not always match the old C tokenizer and that must have been much slower. I assume that is was not seen as suitable for IDLE colorizer. However, the current exposed C tokenizer is being used to power the new PyREPL colorizer. The initial (draft) patch copies portions of that colorizer.

My main concerns are compatibility and speed. Some initial questions:

1. The syntax categories in the REPL colorizer are not the same as IDLE's (listed on the Highlights settings page). What are they?
2. IDLE colorizes 10000 lines editor contents as well as single interactive lines. Will the PR colorizer do the same, with similar speed?
3. Is REPL colorizer stable? Are there open bug reports? (Should be labelled topic-repl.) The code is private and undocumented, I presume intentionally, and I do not expect that issues only relevant to IDLE would be welcome.
4. In the IDLE Issues project, colorizer issues are in Highlights section. Does this fix any, or appear to make fixes easier?

Linked PRs

• gh-140337
• gh-152756

Start by comparing IDLE's current regex-based colorizer with the tokenizer-backed PyREPL colorizer and the exposed tokenizer module. Review the linked PRs gh-140337 and gh-152756, then assess syntax-category compatibility, 10,000-line editor performance, REPL colorizer stability, and relevance to the IDLE Highlights issues.