Complete Joda-Time to java.time migration (#3039)

This completes the exhaustive refactoring of foundational temporal types from Joda-Time to the native java.time API across the entire codebase.

- Replaced org.joda.time.DateTime, Instant, LocalDate, and Duration with java.time equivalents.
- Audited and updated Clock implementations (FakeClock, SystemClock). Added nowMillis(), nowDate(), and nowDateTime() to eliminate repetitive conversions and maintain parallel naming.
- Replaced ZonedDateTime with OffsetDateTime globally per go/avoid-zdt. OffsetDateTime is a better fit as we use a hardcoded ZoneOffset.UTC throughout the system, making geographical time zone rules (like daylight saving time) irrelevant and preventing serialization ambiguities. Added a presubmit check.
- Completely removed all transitional bridge methods from DateTimeUtils and deleted obsolete converters (e.g., DateTimeConverter).
- Updated testing infrastructure, Apache Beam pipelines, custom JCommander parameters, and networking modules to solely rely on java.time primitives.
- Retained the lone necessary org.joda.time.Instant usage in SafeBrowsingTransforms required by the Apache Beam API.
- Cleared Gradle lockfiles and removed the joda-time dependency entirely from the build configuration.

common/src/testing/java/google/registry/testing/FakeClock.java

@@ -21,8 +21,6 @@ import java.time.Duration;
 import java.time.Instant;
 import java.util.concurrent.atomic.AtomicLong;
 import javax.annotation.concurrent.ThreadSafe;
-import org.joda.time.ReadableDuration;
-import org.joda.time.ReadableInstant;
 
 /** A mock clock for testing purposes that supports telling, setting, and advancing the time. */
 @ThreadSafe
@@ -41,12 +39,6 @@ public final class FakeClock implements Clock {
     this(START_INSTANT);
   }
 
-  /** Creates a FakeClock initialized to a specific time. */
-  @Deprecated
-  public FakeClock(ReadableInstant startTime) {
-    setTo(startTime);
-  }
-
   /** Creates a FakeClock initialized to a specific time. */
   public FakeClock(Instant startTime) {
     setTo(startTime);
@@ -66,12 +58,6 @@ public final class FakeClock implements Clock {
    * @param autoIncrementStep the new auto increment duration
    * @return this
    */
-  @Deprecated
-  public FakeClock setAutoIncrementStep(ReadableDuration autoIncrementStep) {
-    this.autoIncrementStepMs = autoIncrementStep.getMillis();
-    return this;
-  }
-
   /**
    * Sets the increment applied to the clock whenever it is queried. The increment is zero by
    * default: the clock is left unchanged when queried.
@@ -91,23 +77,11 @@ public final class FakeClock implements Clock {
     advanceBy(Duration.ofMillis(1));
   }
 
-  /** Advances clock by some duration. */
-  @Deprecated
-  public void advanceBy(ReadableDuration duration) {
-    currentTimeMillis.addAndGet(duration.getMillis());
-  }
-
   /** Advances clock by some duration. */
   public void advanceBy(Duration duration) {
     currentTimeMillis.addAndGet(duration.toMillis());
   }
 
-  /** Sets the time to the specified instant. */
-  @Deprecated
-  public void setTo(ReadableInstant time) {
-    currentTimeMillis.set(time.getMillis());
-  }
-
   /** Sets the time to the specified instant. */
   public void setTo(Instant time) {
     currentTimeMillis.set(time.toEpochMilli());