feat(kernel/expr): add hash_bi function that takes binder information into account
fix(frontends/lean/info_manager): crash when accessing INFO in the end of the file
feat(frontends/lean/server): sort exact matches by size in FINDP
fix(emacs/lean-company): handle singleton candidate case

If we have a singleton auto-complete candidate (e.g. proof_irrel) and it
does not matched with input prefix (e.g. foo), we add the input
prefix (foo) as an extra candidate to prevent the
candidate (proof_irrel) from being automatically selected and completed.
checkpoint
checkpoint2