Run snyk check in periodic build for each development branch (elastic#133751)

we filter by regex for common name pattern of the dev branches to reduce
risk of running from development branch. in reality those periodic builds are
not likely to be triggered by developers so this is a good enough compromise.

Branches that are not developed anymore will stay in snyk for now and require
manual removal.

Author: breskeby

.buildkite/pipelines/periodic.template.yml

@@ -246,7 +246,7 @@ steps:
       image: family/elasticsearch-ubuntu-2404
       machineType: n2-standard-8
       buildDirectory: /dev/shm/bk
-    if: build.branch == "main" || build.branch == "9.1" || build.branch == "9.0" || build.branch == "8.19" || build.branch == "8.18" || build.branch == "7.17"
+    if: build.branch =~ /^(main|\d+\.\d+|\d+\.x)$/
   - label: check-branch-consistency
     command: .ci/scripts/run-gradle.sh branchConsistency
     timeout_in_minutes: 15

.buildkite/pipelines/periodic.yml

@@ -665,7 +665,7 @@ steps:
       image: family/elasticsearch-ubuntu-2404
       machineType: n2-standard-8
       buildDirectory: /dev/shm/bk
-    if: build.branch == "main" || build.branch == "9.1" || build.branch == "9.0" || build.branch == "8.19" || build.branch == "8.18" || build.branch == "7.17"
+    if: build.branch =~ /^(main|\d+\.\d+|\d+\.x)$/
   - label: check-branch-consistency
     command: .ci/scripts/run-gradle.sh branchConsistency
     timeout_in_minutes: 15