Rollup merge of #56945 - JohnHeitmann:rustdoc-js-tester-fix, r=GuillaumeGomez
Rollup merge of #56945 - JohnHeitmann:rustdoc-js-tester-fix, r=GuillaumeGomez

Fix rustdoc-js tests

Fixes rustdoc-js tests by teaching tester.js how to handle single-line js comments.

Also, added speculative support for template strings, and warnings for future debuggers.

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