Change commit log bucket counts in tests

I'm setting it to three buckets across all tests, because the default one bucket
wasn't realistic enough, and allowed some tests to pass that shouldn't have,
essentially by accident.

This also changes RegistryConfig from being an interface to being an abstract
base class. The medium term goal here is to have it be a static class so that it
can provide fields from the YAML-derived POJO in situations where Dagger
injection isn't feasible.

The expected end state is as follows:

default-config.yaml -- The master config file that provides defaults for all
values.

nomulus-config.yaml -- A per-environment config file that overrides the defaults
from the previous file.

YamlConfig.java -- The POJO that the aforementioned YAML files are deserialized
into.

RegistryConfig.java -- Contains a static, memoized instance of YamlConfig and
provides static methods for getting some of those values.

ConfigModule -- Will become a static inner class of RegistryConfig, using Dagger
to provide most of the fields from the memoized YamlConfig instance. This way,
all configuration will be coming from a single place: RegistryConfig.java.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=143567288

javatests/google/registry/model/ofy/CommitLogCheckpointTest.java

@@ -19,12 +19,10 @@ import static google.registry.util.DateTimeUtils.START_OF_TIME;
 import static org.joda.time.DateTimeZone.UTC;
 
 import com.google.common.collect.ImmutableMap;
-import google.registry.config.TestRegistryConfig;
 import google.registry.testing.AppEngineRule;
 import google.registry.testing.ExceptionRule;
 import google.registry.testing.RegistryConfigRule;
 import org.joda.time.DateTime;
-import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -49,16 +47,6 @@ public class CommitLogCheckpointTest {
   private static final DateTime T2 = START_OF_TIME.plusMillis(1);
   private static final DateTime T3 = START_OF_TIME.plusMillis(2);
 
-  @Before
-  public void before() {
-    // Use 3 buckets to make the tests below more realistic.
-    configRule.override(new TestRegistryConfig() {
-      @Override
-      public int getCommitLogBucketCount() {
-        return 3;
-      }});
-  }
-
   @Test
   public void test_getCheckpointTime() {
     DateTime now = DateTime.now(UTC);
@@ -74,18 +62,6 @@ public class CommitLogCheckpointTest {
     assertThat(checkpoint.getBucketTimestamps()).containsExactly(1, T1, 2, T2, 3, T3);
   }
 
-  @Test
-  public void test_getBucketTimestamps_whenOnlyOneBucket_stillWorks() {
-    configRule.override(new TestRegistryConfig() {
-      @Override
-      public int getCommitLogBucketCount() {
-        return 1;
-      }});
-    CommitLogCheckpoint checkpoint =
-        CommitLogCheckpoint.create(DateTime.now(UTC), ImmutableMap.of(1, T1));
-    assertThat(checkpoint.getBucketTimestamps()).containsExactly(1, T1);
-  }
-
   @Test
   public void test_create_notEnoughBucketTimestamps_throws() {
     thrown.expect(IllegalArgumentException.class, "Bucket ids are incorrect");