6907: Lifetime reference search r=matklad a=Veykril
PR #6787 but rewritten to make use of the HIR now. This only applies to Lifetimes, not labels. Also Higher-Ranked Trait Bounds aren't supported yet, but I feel like this PR is big enough as is which is why I left them out after noticing I forgot about them.
Supporting renaming required slight changes in the renaming module as lifetime names aren't allowed for anything but lifetimes(and labels) and vice versa for normal names.
Co-authored-by: Lukas Wirth <lukastw97@gmail.com>
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