[backport#11686#11706] Make ISSUE_TEMPLATE a bit shorter, mention hardware tests

Summary:
ea3f363aa Make ISSUE_TEMPLATE a bit shorter, mention hardware tests (Matt Corallo)

Pull request description:

Kinda getting tired of "block checksum mismatch error" issues on RPis that dont even have heatsinks...Also a shorter issue template might encourage people to actually read it.

e89adba Make default issue text all comments to make issues more readable (Matt Corallo)

Backport of Core PR11686 and PR11706

Test Plan: read it

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8171