Tracking issue for macro :lifetime matcher

[durka]

This tracks the macro_lifetime_matcher feature which provides a :lifetime matcher for macro_rules.

• Implemented in Allow lifetimes in macros #46895.
• Stabilize?

[durka]

Found an ICE.

[petrochenkov]

@durka
There's a tracking issue (#34303) and it even completed FCP. Someone should send a stabilization PR.

[durka]

Oh, I'll do it then instead of updating the tracking issue number.