chore: PR template and validation updates

[michalChrobot]

Purpose of this PR

This PR aims to increase the quality of our PRs by enforcing certain considerations and setting examples via PR template. This will also help with Playtesting and validation of our changes by providing a better way to evaluate PRs for potential playtest specification or release blocking.
It is similar to an "official" suggestion from https://github.com/orgs/community/discussions/84771

New PR template will be working as a "guide" on what would be nice to have in it but the content in the template is more of an example. What matters are sections:

1. Documentation --> Should describe what documentation changes/corrections followed the code changes. This aims to help catching any missing docs but if no documentation changes (API docs, Documentation~) were needed then you can just acknowledge this fact in this section
2. Testing and QA --> Should explain what testing coverage was added for the code changes. This helps to understand if a given change will require playtesting or is it fully covered by automated tests. This can range from "a new sample was created with..." to "edge case issue that is covered by added automated test". Note that WE SHOULD ALMOST ALWAYS add some form of testing. The proposed content of this section helps to see if you performed some manual testing (if you created some project it's always worth linking but no need), it also helps with with general evaluation of changes.
3. Backport --> A section that we already have. Should enforce consideration if those changes should be ported to develop/develop-2.0.0 branches respectively
4. Jira ticket section was added for consideration if such PR is big enough to require Jira ticket present. Note that this section is not mandatory but may be flagged by QA when evaluating PRs for release. I would assume that if PR takes more than a day of work then it should have a corresponding Jira ticket

Those sections make it WAY easier to evaluate PRs that landed when we want to release the package. It allows to see developer thinking on important areas and works as a reminder for them so in case of looking at the PRs it's easier for the QA to analyze those.
Important to note are :

• PR template was updated with more sections where Documentation, Testing and QA, and Backport sections are REQUIRED for a PR to be merged.
• I renamed the git workflow and I will update the name in the settings when merging this PR so for now you can see backport-verification pending since it doesn't exist anymore.
• Testing and Documentation section was basically divided into separate Documentation and Testing and QA sections

Such updated PR template will look as follows

Jira ticket

MTT-12822

Documentation

No documentation changes or additions were necessary.

Testing & QA

This change won't affect users and focuses around our workflow and templates so no testing is needed

Backport

#3583

[NoelStephensUnity]

👍