path: use the next `display` argument to deal with boolean We have a generic mechanism that we can now use for the special case now.

path: display proper user facing value for pulled-delta-reuse-policy The integer was not what the user expect nor what could be provided as a config value.

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`

re2: fix reporting of availability in `hg debuginstall` We add and use an official API to check is re2 is available. This prevent the bug previously in place were debuginstall was considering confusing `None` (i.e. non-initialized) and `False` (i.e. unavailable).

re: make _checkre2 a static method There is no need to it to be a method, so we make it at least a static method to make it easier to call.

re2: exit `_checkre2` early if calling it is useless If we already know if re2 is supported there is no need to run the check again. Stricly speaking we don't call it twice, but this seems a simple enough safeguard to include in this series.