Update oasis-sdk CI to use setup-cli-action (once it's stable/complete)

[ptrus]

I've found two cases in our repos where CLI action is currently manually installed:

• https://github.com/oasisprotocol/oasis-sdk/blob/b63e0da867b8fb02118d28584f4d4a6e79c2a0a9/.github/workflows/release-rofl-scheduler.yml#L18
• https://github.com/oasisprotocol/oasis-sdk/blob/b63e0da867b8fb02118d28584f4d4a6e79c2a0a9/.github/workflows/ci-examples.yml#L65

These two cases can be updated to use the new action.