GH Workflows: Refactor label workflows

Jenkins builds are now triggered on adding label event.
There are 2 possibilites to trigger Jenkins build on PRs from untrusted
authors:
1. Ci-Requested label:
  * one-time permission for given commit
  * label is automatically removed when PR is modified
  * reviewer has to add Ci-Requested label after PR is modified to
    trigger Jenkins build
2. Ci-trusted-author label:
  * permission for given PR
  * label is removed and added again after PR is modified - this sends
    new webhook
  * Jenkins build is triggered automaically after PR is modified

Signed-off-by: Jan Gałda <[email protected]>

.github/workflows/reapply-ci-trusted-author.yml

@@ -0,0 +1,24 @@
+name: Reapply CI-trusted-author label
+
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize]
+
+jobs:
+  remove_label:
+    if: ${{ contains(github.event.*.labels.*.name, 'CI-trusted-author') }}
+    runs-on: ubuntu-latest
+    name: Remove label
+    steps:
+      - name: Remove CI-trusted-author label
+        uses: buildsville/[email protected]
+        with:
+          token: '${{ secrets.GITHUB_TOKEN }}'
+          labels: CI-trusted-author
+          type: remove
+      - name: Add CI-trusted-author label
+        uses: buildsville/[email protected]
+        with:
+          token: '${{ secrets.GITHUB_TOKEN }}'
+          labels: CI-trusted-author
+          type: add