Replace WORKFLOW_PAT with github-app-token

[fabriziosestito]

The following repositories are using the WORKFLOW_PAT secret to dispatch workflows in the helm chart repositories:

• kwctl
• kubewarden-controller
• audit-scanner
• policy-server

AC:

• Replace the WORKFLOW_PAT with the create-github-app-token action in all the above repositories
• Double-check that the secret is not used anywhere else
• Remove the WORKFLOW_PAT secret

[viccuad]

Would be nice to rename the bot account somehow, for it to not be kubewarden-auth-token-generator but something more fitting (e.g: see the user of this PR).