Rollup merge of rust-lang#107058 - clubby789:eqeq-homoglyph, r=wesleywiser

Recognise double-equals homoglyph

Recognise `⩵` as a homoglyph for `==`.

The first commit switches `char` to `&str`, as all previous homoglyphs corresponded to a single ASCII character, while the second implements the fix.

`@rustbot` label +A-diagnostics +A-parser

Author: matthiaskrgr