Token count calculation

Problem/Motivation

Token count calculation is a common feature which could be included in ai_utilities.

I calculate basic token count of code here: https://git.drupalcode.org/project/aidev/-/blob/1.0.x/src/Source.php?ref...
And also have a feature request to calculate prompt token count here ✨ Calculate prompt token count Active
It would be nice to improve prompt count calculation to make it more accurate, because basic calculation averages are different for text/code/etc.
Token calculation could also take into account nuances of different LLMs.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes