docs: update PR template

[mkbreuningIOHK]

What was changed and what it is solving

Related to ATL-7849. The PR template needed to be updated taking the feedback from the engineers into account.
The PR you are reading now is using the proposed PR template.
The changes are:

• Simplify by keeping two sections only: what is changed and how it was tested
• Remove the checklist
• Use HTML comments instead
• Add a markdown block section to trigger a discussion on the automation for release note

How it was tested

The proposed PR was copied and pasted to this actual PR to see the preview.

Release Notes / Changelog

None

[mkbreuningIOHK]

Open for discussion: the markdown block to highlight user facing information for the changelog or release note.
It could be used for automation to create release notes from those sections only.
I saw a few repositories doing that. E.g: Kubernetes and Dockers
We can remove it in a first iteration but I thought it is a good idea. Like adding breaking change there.

[yshyn-iohk]

nice template, @mkbreuningIOHK
In my opinion, it's too lengthy.
Let's see how it will work and collect feedback from other engineers.

[github-actions]

Integration Test Results

 5 files  ±0   5 suites  ±0   12s ⏱️ -1s
17 tests ±0  17 ✅ ±0  0 💤 ±0  0 ❌ ±0 
20 runs  ±0  20 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 4b0454a. ± Comparison against base commit f7cb882.

[FabioPinheiro]

I was thinking for something more like this

**PLEASE REMOVE THIS TEMPLATE BEFORE SUBMITTING**

If it's your first PR on this repository you should:
- Read the [project's guideline](https://github.com/hyperledger/identus/blob/main/CONTRIBUTING.md).

Please ensure that:
- PR title MUST follow the [conventional commit specification](https://www.conventionalcommits.org/en/v1.0.0/).
- PR description MUST have a short summarize of the changes submitted. Including reference any issue/ticket/PR/ADR (Architecture Decision Record) relevant.
- All commit MUST be [Sing (GPG)](???) and free of Copyright [DCO](???)
- When adding third-party dependencies it MUST be included in the [Allowlist](https://toc.hyperledger.org/governing-documents/allowed-third-party-license-policy.html#approved-licenses-for-allowlist).

Thanks for submitting a Pull Request and help make this project awesome! :rocket: :stars:

🚀 🌕
🚀 🌠

[mkbreuningIOHK]

Just to make sure, it is not lengthy for the real PR as the HTML block were used: when you change to preview, all will be removed automatically: so there is no need for the user to remove anything.
This is how it looks when you click on Preview and the source when it is opened for the first time. See screenshots below.

What I can do is simplify the text under the HTML block with the input from @FabioPinheiro

a PR is opened for the first time will show:

[FabioPinheiro]

I don't mine. But "PLEASE REMOVE THIS TEMPLATE BEFORE SUBMITTING" is also like that acknowledge that you read that.