CI(release): add time to RC PR branch names (#11547)

## Problem

We can't have more than one open release PR created on the same day (due
to non-unique enough branch names).

## Summary of changes
- Add time (hours and minutes) to RC PR branch names
- Also make sure we use UTC for releases

.github/workflows/_create-release-pr.yml

@@ -53,10 +53,13 @@ jobs:
             || inputs.component-name == 'Compute' && 'release-compute'
           }}
       run: |
-        today=$(date +'%Y-%m-%d')
-        echo "title=${COMPONENT_NAME} release ${today}" | tee -a ${GITHUB_OUTPUT}
-        echo "rc-branch=rc/${RELEASE_BRANCH}/${today}"  | tee -a ${GITHUB_OUTPUT}
-        echo "release-branch=${RELEASE_BRANCH}"         | tee -a ${GITHUB_OUTPUT}
+        now_date=$(date -u +'%Y-%m-%d')
+        now_time=$(date -u +'%H-%M-%Z')
+        {
+          echo "title=${COMPONENT_NAME} release ${now_date}"
+          echo "rc-branch=rc/${RELEASE_BRANCH}/${now_date}_${now_time}"
+          echo "release-branch=${RELEASE_BRANCH}"
+        } | tee -a ${GITHUB_OUTPUT}
 
     - name: Configure git
       run: |