Update pull request template to suggest making PRs editable by maintainers

Often there are small "nitpicky" changes that need to be done to a PR in order to
get it merged. To speed up the merge process, we will ask contributors
if they are ok with the reviewer making those changes.

Other fixups:
Improve PR template rendering in browser's textarea field. Line wrapping at 80
characters provides a bad user experience within the browser, which
handles word wrapping separately. Thus, prefer long lines in this
markdown file.

Remove the "backwards compatibility section". While the contributor
should ideally care about the impact of their patch on the server's
backwards compatibility, this is an advanced topic that is better
presented in a separate document.

Author: cvicentiu

.github/pull_request_template.md

@@ -1,61 +1,47 @@
 <!--
 Thank you for contributing to the MariaDB Server repository!
 
-You can help us review your changes faster by filling this template <3
+You can help us review your changes faster by filling in this template <3
 
-If you have any questions related to MariaDB or you just want to
-hang out and meet other community members, please join us on
-https://mariadb.zulipchat.com/ .
+If you have any questions related to MariaDB or you just want to hang out and meet other community members, please join us on https://mariadb.zulipchat.com/ .
 -->
 
 <!--
-If you've already identified a https://jira.mariadb.org/ issue
-that seems to track this bug/feature, please add its number below.
+If you've already identified a https://jira.mariadb.org/ issue that seems to track this bug/feature, please add its number below.
 -->
-- [x] *The Jira issue number for this PR is: MDEV-_____*
+- [x] *The Jira issue number for this PR is: MDEV-______*
 
 <!--
 An amazing description should answer some questions like:
 1. What problem is the patch trying to solve?
-2. If some output changed, what was it looking like before
-   the change and how it's looking with this patch applied
-3. Do you think this patch might introduce side-effects in
-   other parts of the server?
+2. If some output changed that is not visible in a test case, what was it looking like before the change and how it's looking with this patch applied?
+3. Do you think this patch might introduce side-effects in other parts of the server?
 -->
 ## Description
 TODO: fill description here
 
 ## How can this PR be tested?
 
-TODO: modify the automated test suite to verify that the PR causes MariaDB to
-behave as intended. Consult the documentation on
-["Writing good test cases"](https://mariadb.org/get-involved/getting-started-for-developers/writing-good-test-cases-mariadb-server).
-In many cases, this will be as simple as modifying one `.test` and one `.result`
-file in the `mysql-test/` subdirectory. Without _automated_ tests, future regressions
-in the expected behavior can't be automatically detected and verified.
+TODO: modify the automated test suite to verify that the PR causes MariaDB to behave as intended.
+Consult the documentation on ["Writing good test cases"](https://mariadb.org/get-involved/getting-started-for-developers/writing-good-test-cases-mariadb-server).
+<!--
+In many cases, this will be as simple as modifying one `.test` and one `.result` file in the `mysql-test/` subdirectory.
+Without automated tests, future regressions in the expected behavior can't be automatically detected and verified.
+-->
 
-If the changes are not amenable to automated testing, please explain why not and
-carefully describe how to test manually.
+If the changes are not amenable to automated testing, please explain why not and carefully describe how to test manually.
 
 <!--
-Tick one of the following boxes [x] to help us understand
-if the base branch for the PR is correct
-(Currently the earliest maintained branch is 10.3)
+Tick one of the following boxes [x] to help us understand if the base branch for the PR is correct. (Currently the earliest maintained branch is 10.3)
 -->
 ## Basing the PR against the correct MariaDB version
-- [ ] *This is a new feature and the PR is based against the latest MariaDB development branch*
-- [ ] *This is a bug fix and the PR is based against the earliest maintained branch in which the bug can be reproduced*
+- [ ] *This is a new feature and the PR is based against the latest MariaDB development branch.*
+- [ ] *This is a bug fix and the PR is based against the earliest maintained branch in which the bug can be reproduced.*
 
 <!--
-You might consider answering some questions like:
-1. Does this affect the on-disk format used by MariaDB?
-2. Does this change any behavior experienced by a user
-   who upgrades from a version prior to this patch?
-3. Would a user be able to start MariaDB on a datadir
-   created prior to your fix?
+  All code merged into the MariaDB codebase must meet a quality standard and codying style.
+  Maintainers are happy to point out inconsistencies but in order to speed up the review and merge process we ask you to check the CODING standards.
 -->
-## Backward compatibility
-TODO: fill details here, if applicable, or remove the section
-
 ## PR quality check
 - [ ] I checked the [CODING_STANDARDS.md](https://github.com/MariaDB/server/blob/11.0/CODING_STANDARDS.md) file and my PR conforms to this where appropriate.
+- [ ] For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.