Our token-based rules and `noqa` extraction used an `Indexer` that kept
track of f-string ranges but not t-strings. We've updated the `Indexer`
and downstream uses thereof to handle both f-strings and t-strings.
Most of the diff is renaming and adding tests.
Note that much of the "new" logic gets to be naive because the lexer has
already ensured that f and t-string "starts" are paired with their
respective "ends", even amidst nesting and so on.
Finally: one could imagine wanting to know if a given interpolated
string range corresponds to an f-string or a t-string, but I didn't find
a place where we actually needed this.
Closes#20310
b6bd32d9dc