Remove oshi-related code from shared agent code (#2682)

instrumentation/oshi/javaagent/oshi-javaagent.gradle

@@ -9,6 +9,7 @@ muzzle {
 }
 
 dependencies {
+  api project(':javaagent-spi')
   implementation project(':instrumentation:oshi:library')
 
   library group: 'com.github.oshi', name: 'oshi-core', version: '5.3.1'

instrumentation/oshi/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/oshi/OshiMetricsInstaller.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.instrumentation.oshi;
+
+import com.google.auto.service.AutoService;
+import io.opentelemetry.instrumentation.api.config.Config;
+import io.opentelemetry.javaagent.spi.ComponentInstaller;
+import java.lang.reflect.Method;
+import java.util.Collections;
+
+/**
+ * {@link ComponentInstaller} to enable oshi metrics during agent startup if oshi is present on the
+ * system classpath.
+ */
+@AutoService(ComponentInstaller.class)
+public class OshiMetricsInstaller implements ComponentInstaller {
+  @Override
+  public void afterByteBuddyAgent(Config config) {
+    if (config.isInstrumentationEnabled(Collections.singleton("oshi"), true)) {
+      try {
+        // Call oshi.SystemInfo.getCurrentPlatformEnum() to activate SystemMetrics.
+        // Oshi instrumentation will intercept this call and enable SystemMetrics.
+        Class<?> oshiSystemInfoClass =
+            ClassLoader.getSystemClassLoader().loadClass("oshi.SystemInfo");
+        Method getCurrentPlatformEnumMethod =
+            oshiSystemInfoClass.getMethod("getCurrentPlatformEnum");
+        getCurrentPlatformEnumMethod.invoke(null);
+      } catch (Throwable ex) {
+        // OK
+      }
+    }
+  }
+}

instrumentation/oshi/javaagent/src/test/groovy/io/opentelemetry/javaagent/instrumentation/oshi/OshiTest.groovy

@@ -9,17 +9,11 @@ import static java.util.concurrent.TimeUnit.SECONDS
 
 import com.google.common.base.Stopwatch
 import io.opentelemetry.instrumentation.test.AgentInstrumentationSpecification
-import oshi.PlatformEnum
-import oshi.SystemInfo
 
 class OshiTest extends AgentInstrumentationSpecification {
 
   def "test system metrics is enabled"() {
-    setup:
-    PlatformEnum platform = SystemInfo.getCurrentPlatformEnum()
-
     expect:
-    platform != null
     // TODO (trask) is this the instrumentation library name we want?
     findMetric("io.opentelemetry.instrumentation.oshi", "system.disk.io") != null
     findMetric("io.opentelemetry.instrumentation.oshi", "system.disk.operations") != null

javaagent-bootstrap/src/main/java/io/opentelemetry/javaagent/OpenTelemetryAgent.java

@@ -67,17 +67,6 @@ public class OpenTelemetryAgent {
       System.err.println("ERROR " + thisClass.getName());
       ex.printStackTrace();
     }
-
-    try {
-      // Call oshi.SystemInfo.getCurrentPlatformEnum() to activate SystemMetrics.
-      // Oshi instrumentation will intercept this call and enable SystemMetrics.
-      Class<?> oshiSystemInfoClass =
-          ClassLoader.getSystemClassLoader().loadClass("oshi.SystemInfo");
-      Method getCurrentPlatformEnumMethod = oshiSystemInfoClass.getMethod("getCurrentPlatformEnum");
-      getCurrentPlatformEnumMethod.invoke(null);
-    } catch (Throwable ex) {
-      // OK
-    }
   }
 
   private static synchronized URL installBootstrapJar(Instrumentation inst)