Add language parameter to Text objects

[QuLogic]

PR summary

Along with #29695, this language parameter is an additional setting that may affect text layout. As with the other PR, this is not complete, but rather something to get the API decided upon (and likely will be rebased on raqm PR after it's done.)

There are two parts to the API:

1. the language parameter attached to Text, and any other API that wraps it (i.e., Axes.text or Axes.annotate)
2. the language parameter in backend's Renderer.draw_text

At the moment, for both, I have set these to str | list[tuple[str, int, int]] where the latter denotes a list of (language, start, end)-tuples. However, this was before I found out about the font feature machinery, and it is possible that we may wish to use that syntax instead, at least for API part 1. For part 2, it's a little nicer to have the explicit types, just for passing to the FT2Font extension, but this may not be relevant to other implementations.

PR checklist

• [n/a] "closes #0000" is in the body of the PR description to link the related issue
• new and changed code is tested
• Plotting related features are demonstrated in an example
• New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

[anntzer]

re: adding language to draw_text: the general discussion about extensibility of renderer API applies, i.e.

• if you're going to add language as a parameter to draw_text then it should be at least keyword-only.
• it's likely that the more maintainable API would likely to just embed language as part of fontproperties (it's not really different from e.g. font features, I'd think) and tell the backend to read that info.
• for draw_text we have actually more or less given up on having a "clean" renderer API because we pass the whole Text instance to draw_text (per Propagate mpl.text.Text instances to the backends and fix documentation #1081) anyways so perhaps backends that care could also just read that info off the Text instance. It feels a bit dirty, but heh... ("dirty" because we as well may just have a renderer API that's renderer.draw_text(textobj) to start with...)

[anntzer]

Side point regarding allowing list[tuple[str, int, int]] as language setting: this may be a problem if one uses somelanguage[idx:] to set the language from an index up to the end of the string (whose length could technically be modified later, even though it's not clear this necessarily makes much practical sense). Likely you need list[tuple[str, int, int | None]] (and then you may possibly support None (=0) for the start as well).