[Profiling] Annotate TODOs for 9.0.0 upgrade

As suggested by David in elastic#106592, we're adding the annotation
`@UpdateForV9` to all places in the Universal Profiling plugin that
can be removed once we move to 9.0.0.

Relates elastic#106592

x-pack/plugin/profiling/src/main/java/org/elasticsearch/xpack/profiling/CO2Calculator.java

@@ -7,6 +7,8 @@
 
 package org.elasticsearch.xpack.profiling;
 
+import org.elasticsearch.core.UpdateForV9;
+
 import java.util.Map;
 
 final class CO2Calculator {
@@ -52,6 +54,7 @@ public double getAnnualCO2Tons(String hostID, long samples) {
         return getKiloWattsPerCore(host) * getCO2TonsPerKWH(host) * annualCoreHours * getDatacenterPUE(host);
     }
 
+    @UpdateForV9 // only allow OTEL semantic conventions
     private double getKiloWattsPerCore(HostMetadata host) {
         return switch (host.hostArchitecture) {
             // For the OTEL donation of the profiling agent, we switch to OTEL semantic conventions,

x-pack/plugin/profiling/src/main/java/org/elasticsearch/xpack/profiling/GetFlamegraphResponse.java

@@ -13,6 +13,7 @@
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.xcontent.ChunkedToXContentHelper;
 import org.elasticsearch.common.xcontent.ChunkedToXContentObject;
+import org.elasticsearch.core.UpdateForV9;
 import org.elasticsearch.xcontent.ToXContent;
 
 import java.io.IOException;
@@ -24,7 +25,9 @@ public class GetFlamegraphResponse extends ActionResponse implements ChunkedToXC
     private final int size;
     private final double samplingRate;
     private final long selfCPU;
+    @UpdateForV9 // remove this field - it is unused in Kibana
     private final long totalCPU;
+    @UpdateForV9 // remove this field - it is unused in Kibana
     private final long totalSamples;
     private final List<Map<String, Integer>> edges;
     private final List<String> fileIds;

x-pack/plugin/profiling/src/main/java/org/elasticsearch/xpack/profiling/GetStackTracesResponse.java

@@ -14,6 +14,7 @@
 import org.elasticsearch.common.xcontent.ChunkedToXContentHelper;
 import org.elasticsearch.common.xcontent.ChunkedToXContentObject;
 import org.elasticsearch.core.Nullable;
+import org.elasticsearch.core.UpdateForV9;
 import org.elasticsearch.xcontent.ToXContent;
 
 import java.util.Collections;
@@ -29,8 +30,10 @@ public class GetStackTracesResponse extends ActionResponse implements ChunkedToX
     private final Map<String, StackFrame> stackFrames;
     @Nullable
     private final Map<String, String> executables;
+    @UpdateForV9 // remove this field - it is unused in Kibana
     @Nullable
     private final Map<String, TraceEvent> stackTraceEvents;
+    @UpdateForV9 // remove this field - it is unused in Kibana
     private final int totalFrames;
     private final double samplingRate;
     private final long totalSamples;

x-pack/plugin/profiling/src/main/java/org/elasticsearch/xpack/profiling/HostMetadata.java

@@ -7,6 +7,7 @@
 
 package org.elasticsearch.xpack.profiling;
 
+import org.elasticsearch.core.UpdateForV9;
 import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
 
@@ -30,6 +31,7 @@ final class HostMetadata implements ToXContentObject {
         this.profilingNumCores = profilingNumCores != null ? profilingNumCores : DEFAULT_PROFILING_NUM_CORES;
     }
 
+    @UpdateForV9 // remove fallback to the "profiling.host.machine" field and remove it from the component template "profiling-hosts".
     public static HostMetadata fromSource(Map<String, Object> source) {
         if (source != null) {
             String hostID = (String) source.get("host.id");

x-pack/plugin/profiling/src/main/java/org/elasticsearch/xpack/profiling/InstanceType.java

@@ -7,6 +7,7 @@
 
 package org.elasticsearch.xpack.profiling;
 
+import org.elasticsearch.core.UpdateForV9;
 import org.elasticsearch.xcontent.ToXContentObject;
 import org.elasticsearch.xcontent.XContentBuilder;
 
@@ -73,6 +74,7 @@ public static InstanceType fromHostSource(Map<String, Object> source) {
         return new InstanceType(provider, region, null);
     }
 
+    @UpdateForV9 // remove this method
     private static InstanceType fromObsoleteHostSource(Map<String, Object> source) {
         // Check and handle AWS.
         String region = (String) source.get("ec2.placement.region");