Remove legacy field injection code

Author: mcculls

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/FieldBackedContextStoreAppliedMarker.java

@@ -8,7 +8,6 @@
 import static net.bytebuddy.matcher.ElementMatchers.none;
 
 import datadog.trace.agent.tooling.context.FieldBackedContextProvider;
-import datadog.trace.agent.tooling.context.FieldBackedProvider;
 import datadog.trace.api.Config;
 import datadog.trace.bootstrap.FieldBackedContextAccessor;
 import datadog.trace.bootstrap.instrumentation.java.concurrent.ExcludeFilter;
@@ -77,11 +76,7 @@ public static ResettableClassFileTransformer installBytebuddyAgent(
       final AgentBuilder.Listener... listeners) {
     INSTRUMENTATION = inst;
 
-    if (Config.get().isLegacyContextFieldInjection()) {
-      FieldBackedProvider.resetContextMatchers();
-    } else {
-      FieldBackedContextProvider.resetContextMatchers();
-    }
+    FieldBackedContextProvider.resetContextMatchers();
 
     AgentBuilder.Ignored ignoredAgentBuilder =
         new AgentBuilder.Default()

dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/AgentInstaller.java

@@ -11,7 +11,6 @@
 import datadog.trace.agent.tooling.bytebuddy.DDTransformers;
 import datadog.trace.agent.tooling.bytebuddy.ExceptionHandlers;
 import datadog.trace.agent.tooling.context.FieldBackedContextProvider;
-import datadog.trace.agent.tooling.context.FieldBackedProvider;
 import datadog.trace.agent.tooling.context.InstrumentationContextProvider;
 import datadog.trace.agent.tooling.context.NoopContextProvider;
 import datadog.trace.agent.tooling.muzzle.Reference;
@@ -128,11 +127,7 @@ private void lazyInit() {
             }
           }
           if (!contextStores.isEmpty()) {
-            if (Config.get().isLegacyContextFieldInjection()) {
-              contextProvider = new FieldBackedProvider(this, contextStores);
-            } else {
-              contextProvider = new FieldBackedContextProvider(this, contextStores);
-            }
+            contextProvider = new FieldBackedContextProvider(this, contextStores);
           } else {
             contextProvider = NoopContextProvider.INSTANCE;
           }