REFACTOR `raise_validation_error_from_rule_violation`

Add `raise_validation_error_from_rule_violation` function. This will be
re-used by `_process_input_Call`.
FEATURE `process`

Add `process` function. Accepts a schema of callables, calls each one
with corresponding `data` as keyword arguments, and returns the return
values. `RuleViolation` errors are converted to `RulesValidationError`.
FEATURE `_process_Call`