Fix f-string middle panic when parsing t-strings

[ntBre]

Summary

This PR fixes #23198 by copying Dylan's changes from #19183 to the other
InterpolatedStringElementsKind variant, in line with Micha's prophetic comment (https://github.com/astral-sh/ruff/pull/19183/changes#r2217325217).

Test Plan

Two new tests derived from the issue

[codspeed-hq]

Merging this PR will not alter performance

✅ 54 untouched benchmarks

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_{Comparing brent/f-string-middle (dbe80c2) with main (647f660)}

[astral-sh-bot]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

[ntBre]

Not really sure what happened with the benchmarks, but it cleared up after rebasing on main. There are some ~2% regressions but also some improvements, so I think it's pretty neutral overall, as I would expect.

[dylwil3]

in line with Micha's prophetic comment

truly a red flag that I casually asserted Micha was wrong. we should add a CI check for that.

[dylwil3]

This looks great to me! I'm glad it wasn't too painful.

[dylwil3]

weird that we skipped 27 (did I do that??)
should we just renumber them sequentially or does that break something?

[ntBre]

It was weird, but it wasn't you! It was like that before your PR. I'm assuming one of them got removed at some point?

I vaguely remember trying to reorder a different set of bitflags previously and someone suggested leaving them alone, but I'm happy to do it if you prefer. Maybe @dhruvmanila will have an opinion too.

[dhruvmanila]

I think it's fine to change the values, I'm assuming that we should avoid doing that mainly to make the reviewing easier but I guess you could do it before merging. Anyways, this doesn't look like a big change 🤷‍♂️

[ntBre]

It wasn't painful at all! You had already done the hard work for me 😄

[samuelcolvin]

Thanks so much for this.