CI: unified Linux pipeline (#3855)

Author: mshabunin

.github/workflows/PR-4.x.yaml

@@ -6,18 +6,14 @@ on:
       - 4.x
 
 jobs:
+  Linux:
+    uses: opencv/ci-gha-workflow/.github/workflows/OCV-PR-Linux.yaml@main
+    with:
+      workflow_branch: main
+
   Ubuntu2004-ARM64:
     uses: opencv/ci-gha-workflow/.github/workflows/OCV-Contrib-PR-4.x-ARM64.yaml@main
 
-  Ubuntu2004-x64:
-    uses: opencv/ci-gha-workflow/.github/workflows/OCV-Contrib-PR-4.x-U20.yaml@main
-
-  Ubuntu2204-x64:
-    uses: opencv/ci-gha-workflow/.github/workflows/OCV-Contrib-PR-4.x-U22.yaml@main
-
-  Ubuntu2404-x64:
-    uses: opencv/ci-gha-workflow/.github/workflows/OCV-Contrib-PR-4.x-U24.yaml@main
-
   Ubuntu2004-x64-CUDA:
     uses: opencv/ci-gha-workflow/.github/workflows/OCV-Contrib-PR-4.x-U20-Cuda.yaml@main