fix(tests): align MockServiceRegistry overrides with ServiceRegistry interface

MockServiceRegistry in MetricsRegistry.cpp still used the old method
names (timeKeeper, cachedSLEs, validators, overlay, cluster, app, etc.)
while ServiceRegistry has been standardized on getXxx()/isXxx() forms.
Windows CI caught this as C3668 "did not override any base class methods"
errors and C2259 "cannot instantiate abstract class".

Rename all 13 mismatched overrides to match the current interface:
  timeKeeper          -> getTimeKeeper
  cachedSLEs          -> getCachedSLEs
  validators          -> getValidators
  validatorSites      -> getValidatorSites
  validatorManifests  -> getValidatorManifests
  publisherManifests  -> getPublisherManifests
  overlay             -> getOverlay
  cluster             -> getCluster
  peerReservations    -> getPeerReservations
  pendingSaves        -> getPendingSaves
  openLedger (x2)     -> getOpenLedger
  getPathRequests     -> getPathRequestManager (type rename too)
  journal             -> getJournal
  logs                -> getLogs
  trapTxID            -> getTrapTxID
  app                 -> getApp

Also regenerate levelization ordering.txt to reflect the new
tests.libxrpl -> xrpl.core edge introduced by ServiceRegistry.h include.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.github/scripts/levelization/results/ordering.txt

@@ -191,6 +191,7 @@ test.toplevel > xrpl.json
 test.unit_test > xrpl.basics
 test.unit_test > xrpl.protocol
 tests.libxrpl > xrpl.basics
+tests.libxrpl > xrpl.core
 tests.libxrpl > xrpld.telemetry
 tests.libxrpl > xrpl.json
 tests.libxrpl > xrpl.net