paths: add an argument to format the suboption display We will use it in the next function to the delta policy display. It could also be use to deal with the other special case in the command code, but that is unnecessary churn for stable so that part will go on default.

ui: fix crash in `hg paths` when pulled-delta-reuse-policy is in use The crash is a result of [value] being an int, but being used as a bytestring.

ui: add a test demonstrating a crash in `hg paths`