[chore/github]: Standardize GitHub PR description template

Replace legacy templates with unified pull_request_template.md
(description, type, approach, documentation).

Signed-off-by: Oleksandr Ivantsiv <oivantsiv@nvidia.com>

Author: oleksandrivantsiv

.github/copilot-instructions.md

@@ -83,10 +83,10 @@ pytest tests/ --cov=sonic_platform_base --cov-report=term-missing
 - **Abstract methods**: New abstract methods must have default implementations to avoid breaking subclasses
 - **Documentation**: All new API methods need docstrings
 - **PR description template**: Fill out all sections of the [PR template](.github/pull_request_template.md) when submitting a pull request:
-  - **Description**: Describe your changes in detail
-  - **Motivation and Context**: Why is this change required? What problem does it solve? Reference issues with "fixes #xxxx"
-  - **How Has This Been Tested?**: Describe how you tested your changes, including test environment and tests run
-  - **Additional Information**: Any other relevant details (optional)
+  - **Description of PR**: Summary of the change, motivation/context, reviewer entry point, and dependencies; reference issues with `fixes #xxxx` / `closes #xxxx`.
+  - **Type of change**: Mark the box(es) that apply — bug fix, new feature, refactor / cleanup, documentation update, test improvement.
+  - **Approach**: Motivation; how you did it; how you verified/tested it; any platform-specific notes.
+  - **Documentation**: Link to wiki / doc updates relevant to new features or test cases.
 
 ## Common Patterns
 

.github/pull_request_template.md

@@ -1,23 +1,45 @@
-<!-- Provide a general summary of your changes in the Title above -->
-
-#### Description
 <!--
-     Describe your changes in detail
--->
+Please make sure you've read and understood our contributing guidelines;
+https://github.com/Azure/SONiC/blob/gh-pages/CONTRIBUTING.md
 
-#### Motivation and Context
+Please provide following information to help code review process a bit easier:
+-->
+### Description of PR
 <!--
-     Why is this change required? What problem does it solve?
-     If this pull request closes/resolves an open Issue, make sure you
-     include the text "fixes #xxxx", "closes #xxxx" or "resolves #xxxx" here
+- Please include a summary of the change and which issue is fixed.
+- Please also include relevant motivation and context. Where should reviewer start? background context?
+- List any dependencies that are required for this change.
 -->
 
-#### How Has This Been Tested?
+Summary:
+Fixes # (issue)
+
+### Type of change
+
 <!--
-     Please describe in detail how you tested your changes.
-     Include details of your testing environment, and the tests you ran to
-     see how your change affects other areas of the code, etc.
+- Fill x for your type of change.
+- e.g.
+- [x] Bug fix
 -->
 
-#### Additional Information (Optional)
+- [ ] Bug fix
+- [ ] New feature
+- [ ] Refactor / cleanup
+- [ ] Documentation update
+- [ ] Test improvement
+
+### Approach
+#### What is the motivation for this PR?
 
+#### How did you do it?
+
+#### How did you verify/test it?
+
+#### Any platform specific information?
+
+### Documentation
+<!--
+(If it's a new feature, new test case)
+Did you update documentation/Wiki relevant to your implementation?
+Link to the wiki page?
+-->