Create SGPatroniConfig CRD

The goal of this CRD is to offer the user to (optionally) specify a customized Patroni configuration. For the most part, we will be considering the Dynamic configuration settings, that are stored in the DCS.

This would allow to specify some low-level parameters (like loop_wait, ttl, maximum_lag_on_failover and several others). Not all Patroni parameters will be exposed. As such, we need to create a list containing:

1. Parameters that will be exposed but at higher abstraction layers (for example, the replication type, which will be more explicitly exposed as part of the SGCluster.
2. Parameters that will be blocked (to prevent SG malfunction).
3. Parameters that can be altered, but SG sets with non default values.

In the .status field we should report all values set, similarly to what's being done for other configurations.

This issue is inspired by #838 (closed).