rustdoc: Regression in whitespacing inside macro_rules matchers

[dtolnay]

#[macro_export]
macro_rules! repro {
    ($e:expr, std::path) => {};
}

Before:

This preserves the spacing in the way that the macro author wrote, and exactly the way that they intend for the macro user to write those spaces on their end.

After:

The person calling the macro needs to reverse engineer where to add/delete spaces in order to get a readable result.

I haven't bisected but it seems likely from skimming the implementation that this is related to #86282. Overall I think #86282 would tend to be net negative for the vast majority of macros. @camelid @jyn514 is there perhaps some other way to deal with the edge cases that didn't have proper source code for rustdoc to copy?

[camelid]

Yeah, I know the formatting regressions from that PR were not great, but it fixed a bunch of bugs. In general, I think rustdoc shouldn't be relying on the source code except for the actual source code view.