Refactor some ILM tests to not use deprecated methods (elastic#131417)

And update `MetadataMigrateToDataTiersRoutingService` to accept a
`ProjectState` instead of a `ProjectResolver`.

Author: nielsbauman

server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java

@@ -1490,12 +1490,6 @@ public Builder templates(Map<String, IndexTemplateMetadata> templates) {
             return this;
         }
 
-        @Deprecated(forRemoval = true)
-        public Builder put(String name, ComponentTemplate componentTemplate) {
-            getSingleProject().put(name, componentTemplate);
-            return this;
-        }
-
         @Deprecated(forRemoval = true)
         public Builder componentTemplates(Map<String, ComponentTemplate> componentTemplates) {
             getSingleProject().componentTemplates(componentTemplates);
@@ -1536,12 +1530,6 @@ public boolean put(String aliasName, String dataStream, Boolean isWriteDataStrea
             return getSingleProject().put(aliasName, dataStream, isWriteDataStream, filter);
         }
 
-        @Deprecated(forRemoval = true)
-        public Builder removeDataStream(String name) {
-            getSingleProject().removeDataStream(name);
-            return this;
-        }
-
         public Builder putCustom(String type, ClusterCustom custom) {
             customs.put(type, Objects.requireNonNull(custom, type));
             return this;

x-pack/plugin/ilm/src/main/java/org/elasticsearch/xpack/cluster/metadata/MetadataMigrateToDataTiersRoutingService.java

@@ -11,6 +11,7 @@
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.client.internal.Client;
 import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.ProjectState;
 import org.elasticsearch.cluster.metadata.ComponentTemplate;
 import org.elasticsearch.cluster.metadata.ComposableIndexTemplate;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
@@ -19,10 +20,10 @@
 import org.elasticsearch.cluster.metadata.Metadata;
 import org.elasticsearch.cluster.metadata.ProjectMetadata;
 import org.elasticsearch.cluster.metadata.Template;
-import org.elasticsearch.cluster.project.ProjectResolver;
 import org.elasticsearch.cluster.routing.allocation.DataTier;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.core.NotMultiProjectCapable;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.Tuple;
 import org.elasticsearch.license.XPackLicenseState;
@@ -178,16 +179,15 @@ private MetadataMigrateToDataTiersRoutingService() {}
      * ILM routing allocations. It also returns a summary of the affected abstractions encapsulated in {@link MigratedEntities}
      */
     public static Tuple<ClusterState, MigratedEntities> migrateToDataTiersRouting(
-        ClusterState currentState,
-        ProjectResolver projectResolver,
+        ProjectState currentState,
         @Nullable String nodeAttrName,
         @Nullable String indexTemplateToDelete,
         NamedXContentRegistry xContentRegistry,
         Client client,
         XPackLicenseState licenseState,
         boolean dryRun
     ) {
-        ProjectMetadata currentProjectMetadata = projectResolver.getProjectMetadata(currentState);
+        ProjectMetadata currentProjectMetadata = currentState.metadata();
         if (dryRun == false) {
             IndexLifecycleMetadata currentMetadata = currentProjectMetadata.custom(IndexLifecycleMetadata.TYPE);
             if (currentMetadata != null && currentILMMode(currentProjectMetadata) != STOPPED) {
@@ -197,7 +197,9 @@ public static Tuple<ClusterState, MigratedEntities> migrateToDataTiersRouting(
             }
         }
 
-        Metadata.Builder mb = Metadata.builder(currentState.metadata());
+        @NotMultiProjectCapable // We're doing something fishy here by updating the Metadata even though we're inside the scope of a single
+        // project. This is generally not correct, but since ILM is not properly project-aware, we're making an exception here.
+        Metadata.Builder mb = Metadata.builder(currentState.cluster().metadata());
         ProjectMetadata.Builder newProjectMetadataBuilder = ProjectMetadata.builder(currentProjectMetadata);
 
         // remove ENFORCE_DEFAULT_TIER_PREFERENCE from the persistent settings
@@ -245,7 +247,7 @@ public static Tuple<ClusterState, MigratedEntities> migrateToDataTiersRouting(
             attribute
         );
         return Tuple.tuple(
-            ClusterState.builder(currentState).metadata(mb).putProjectMetadata(newProjectMetadataBuilder).build(),
+            ClusterState.builder(currentState.cluster()).metadata(mb).putProjectMetadata(newProjectMetadataBuilder).build(),
             new MigratedEntities(removedIndexTemplateName, migratedIndices, migratedPolicies, migratedTemplates)
         );
     }

x-pack/plugin/ilm/src/main/java/org/elasticsearch/xpack/ilm/action/TransportMigrateToDataTiersAction.java

@@ -90,10 +90,10 @@ protected void masterOperation(
         ClusterState state,
         ActionListener<MigrateToDataTiersResponse> listener
     ) throws Exception {
+        final var projectId = projectResolver.getProjectId();
         if (request.isDryRun()) {
             MigratedEntities entities = migrateToDataTiersRouting(
-                state,
-                projectResolver,
+                state.projectState(projectId),
                 request.getNodeAttributeName(),
                 request.getLegacyTemplateToDelete(),
                 xContentRegistry,
@@ -131,8 +131,7 @@ protected void masterOperation(
             @Override
             public ClusterState execute(ClusterState currentState) {
                 Tuple<ClusterState, MigratedEntities> migratedEntitiesTuple = migrateToDataTiersRouting(
-                    currentState,
-                    projectResolver,
+                    currentState.projectState(projectId),
                     request.getNodeAttributeName(),
                     request.getLegacyTemplateToDelete(),
                     xContentRegistry,