Update Netty and OkHttp dependencies and resolve test failures (#3066)

This commit updates several dependencies in dependencies.gradle and resolves the resulting test failures:
- Netty: Updated strict upper bound from <4.2.0 to <5.0.0 (resolved to 4.2.14.Final).
- OkHttp: Removed strict upper bound of <5.0.0 and moved to dynamic versions section (resolved to 5.3.2).
- Cleaned up dependencies.gradle by moving strict dependencies (secretmanager, common-protos, gax) out of the dynamic versions section.
- Updated all gradle.lockfile files.

Resulting test fixes:
- Netty: Replaced NioEventLoopGroup with DefaultEventLoopGroup in NettyExtension and ProbingStepTest. In Netty 4.2+, LocalServerChannel no longer supports registration with NIO-backed event loops, throwing an IllegalArgumentException.
- OkHttp: Refactored ServiceMonitoringClient to safely handle empty responses using Optional.orElse(). In OkHttp 5.x, a 204 No Content response returns a non-null ResponseBody with an empty string, causing an assertion failure where MosApiException was incorrectly bypassed.

core/src/main/java/google/registry/mosapi/ServiceMonitoringClient.java

@@ -49,10 +49,10 @@ public class ServiceMonitoringClient {
             tld, MONITORING_STATE_ENDPOINT, Collections.emptyMap(), Collections.emptyMap())) {
 
       ResponseBody responseBody = response.body();
-      if (responseBody == null) {
+      if (responseBody == null || responseBody.contentLength() == 0) {
         throw new MosApiException(
             String.format(
-                "MoSAPI Service Monitoring API " + "returned an empty body with status: %d",
+                "MoSAPI Service Monitoring API returned an empty body with status: %d",
                 response.code()));
       }
       String bodyString = responseBody.string();