ci: concurrency control for CI jobs (frappe#27230)

similar to frappe/frappe#14061

This will ensure that only one instance of the following tests run per
PR and cancel previous running/queued jobs when new commits are pushed.

- Server / unit tests
- UI tests
- Patch test

.github/workflows/patch.yml

@@ -7,6 +7,9 @@ on:
       - '**.md'
   workflow_dispatch:
 
+concurrency:
+  group: patch-develop-${{ github.event.number }}
+  cancel-in-progress: true
 
 jobs:
   test:

.github/workflows/server-tests.yml

@@ -12,6 +12,10 @@ on:
       - '**.js'
       - '**.md'
 
+concurrency:
+  group: server-develop-${{ github.event.number }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: ubuntu-18.04

.github/workflows/ui-tests.yml

@@ -6,6 +6,10 @@ on:
       - '**.md'
   workflow_dispatch:
 
+concurrency:
+  group: ui-develop-${{ github.event.number }}
+  cancel-in-progress: true
+
 jobs:
   test:
     runs-on: ubuntu-18.04