minor tweaks for terminal.py

[symonk]

Some minor tweaks to the terminal.py module, namely:

• Removal of unused args for mywriter and _locationline (tags and lineno respectively), neither appear used
• Some extra typing in places
• Change getreports to use a list comp
• Simplify _getfailureheadline

edit: Other merged PRs have done some of the same work here, so its quite miniscule now

[symonk]

Thanks @bluetech between some reverts & the other PR outlined this ended up being tiny, sorry to take your time for such trivial changes in the end. Appreciate it as always (will make sure to squash if you feel the list comp change is worth while!)