Improve GH actions

[leggerf]

There are a couple of things to fix:

• some checkout actions are outdated
• add another test-benchmarks.yml that runs weekly on devel.

Example here:

name: Release Management
on: 
  schedule:
   - cron: "*/5 * * * *"
jobs:
  build:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
        with:
          ref: some-branch