Add utilities for counting iterables and lazily-compiling regexes.
Review Request #13160 — Created July 25, 2023 and submitted
djblets.util.functional, which offers two useful
iterable_len(): Efficiently computes the length of a finite
lazy_re_compile(): Lazily compiles a regex on first access, reducing
module load time for regexes as class/module attributes.
Unit tests pass.
Used both of these in some in-progress code.