refactor(ocpp): dissolve OCPPServiceUtils class and eliminate dynamic imports

refactor(ocpp): dissolve OCPPServiceUtils class and eliminate dynamic imports

Dissolve the OCPPServiceUtils class into standalone exported functions,
removing the class hierarchy (extends) from OCPP16/20ServiceUtils.

Extract 6 version-dispatching operations into OCPPServiceOperations.ts
with static top-level imports, eliminating all 11 dynamic await import()
calls that were used to work around circular dependencies.

The dependency graph is now a clean DAG:
  OCPPServiceUtils.ts (pure utilities, no version knowledge of subclasses)
  OCPP16/20ServiceUtils.ts (version-specific, import utils directly)
  OCPPServiceOperations.ts (dispatchers, static imports of both)

Cross-component imports now go through barrel files per project conventions.
JSDoc harmonized across all modified files.