ci: Run CI on the versa_ecp5 runner.
This causes CI to only run on runners with the versa_ecp5 tag. A new runner has been created with this tag with a limit of 1 to ensure hw can only be used by one job at a time. The default runner can be used by other jobs that do not need hw access and have a higher job limit.
Note that for other future devices such as the ulx3s, a new tag could be created with customer test rules as well.