simplify issue template, and PR template, and make things optional

## Description

While it's good have standards, sometimes you they don't fit for everything. I think it will be better if:

1. Make it clear that the standards here are optional. When somebody else creates a repo, if they are not bothered with github templates, they can just copy & paste the ones in this repo and use it. But if they do care about the github templates for their projects, then they are allowed to use their own.
2. Simply the PR template. At the moment, it asks too much questions and most of the time people just ignore them anyway. I prefer to just keep it 2 parts:

* Description
* Verification

Or we make most of things commented out initially, and let people uncomment the section they need.