* .github: move pull request template into .github directory
This keeps it out of the root directory. The main intention is
that keeping it out-of-root helps give it less attention which
is enough for the template.
* .github: add a issue form template for the app
This is based on the exisitng issue template of the app. It has
some additional tweaks done to update stale information.
* .github: add some more issue templates
We don't do anything about these ones, and they just clutter the logs making important stuff much harder to find (as agreed in #2823 and #4077).
We already use IntelliJ's inspections feature to replace the need for this.
