Replace top level module by multi-runner (default)

[npalm]

Description

The module has current to main modules to deploy the runners.

• The original top-level one deploying a single runner
• The multi-runner one allowing to deploy multiple runner configurations at once using the same webhook.

Problem having both is complexity. We need to test both. Contributors must be aware to update both modules. And in the end, you can always use the multi-runner, even for a single runner setup.

With the multi-runner setup, you can also run a single runner. Therefore, this proposal will be to swap the modules, make the multi-runner the default one. And keep the single runner in a module for the time span of one major release before phasing it out.