gccrs: Track lifetimes per trait item

Fixes Rust-GCC/gccrs#4861

gcc/rust/ChangeLog:

	* typecheck/rust-hir-type-check.cc (TraitItemReference::get_type_from_fn): grab lifetimes

gcc/testsuite/ChangeLog:

	* rust/compile/issue-4861.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>