Auto merge of #154014 - Unique-Usman:ua/decmacrounrepeatable2, r=estebank

rustc_expand: improve diagnostics for non-repeatable metavars



There was an initally opened pr which solve this issue here rust-lang/rust#152679. It got merged but, there was a perf regression. And this new pr is opened to address the problem. The first did the computation of binding and matched_rule and then passed them as owned value down to `diagnostics::emit_frag_parse_err(` but, now this pr address the issue by passing `lhs` and `rules` as borrowed value to from_tts and the move the logic to `diagnostics::emit_frag_parse_err(`.

Fix rust-lang/rust#47452.

Author: bors