Refactor machine config validation using config manager validation

**What would you like to be added**:
This is a code refactor (no feature added/deleted/updated) so that config manager validator can use reflection to call cloud providers that implement validate interface for machine config validation for static validation.

**Why is this needed**:
The refactor can reduce provider's validator.go ValidateClusterMachineConfigs to only have context aware validation.

Start by locating the config manager validator and provider ValidateClusterMachineConfigs implementations mentioned in the issue. Trace how static and context-aware validation are separated, then verify that providers implementing the validate interface are discovered and invoked through the config manager while provider validation retains only context-aware checks.

Written by the indexing model from the issue text.