Rollup merge of #59156 - davidtwco:issue-55809, r=nikomatsakis
Rollup merge of #59156 - davidtwco:issue-55809, r=nikomatsakis

[wg-async-await] Add regression test for #55809.

Fixes #55809.

This PR adds a regression test for #55809 which checks that a
overflow does not occur when evaluating a requirement for async
functions and `&mut` arguments in some specific circumstances.

aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust