Added new GitHub action for manual integration test run based on PR (#4135)

* Added new GitHub action for manual integration test run based on PR

* Addressed comments

* Added branch name as input

* Small improvements

.github/workflows/python-merge-tests.yml

@@ -2,6 +2,13 @@ name: Python - Merge - Tests
 
 on:
   workflow_dispatch:
+  workflow_call:
+    inputs:
+      checkout-ref:
+        description: "Git ref to checkout (e.g., a commit SHA from a PR)"
+        required: false
+        type: string
+        default: ""
   pull_request:
     branches: ["main"]
   merge_group:
@@ -29,6 +36,8 @@ jobs:
       pythonChanges: ${{ steps.filter.outputs.python}}
     steps:
       - uses: actions/checkout@v6
+        with:
+          ref: ${{ inputs.checkout-ref }}
       - uses: dorny/paths-filter@v3
         id: filter
         with:
@@ -76,6 +85,8 @@ jobs:
         working-directory: python
     steps:
       - uses: actions/checkout@v6
+        with:
+          ref: ${{ inputs.checkout-ref }}
       - name: Set up python and install the project
         id: python-setup
         uses: ./.github/actions/python-setup
@@ -135,6 +146,8 @@ jobs:
         working-directory: python
     steps:
       - uses: actions/checkout@v6
+        with:
+          ref: ${{ inputs.checkout-ref }}
       - name: Set up python and install the project
         id: python-setup
         uses: ./.github/actions/python-setup