feat(gatsby-source-wordpress): Support on plugin init (#33080)

* use onplugininit if core supports it

* fix name

packages/gatsby-source-wordpress/src/constants.ts

@@ -1,3 +1,7 @@
 export const CREATED_NODE_IDS = `WPGQL-created-node-ids`
 export const LAST_COMPLETED_SOURCE_TIME = `WPGQL-last-completed-source-time`
 export const MD5_CACHE_KEY = `introspection-node-query-md5`
+export const INITIALIZE_PLUGIN_LIFECYCLE_NAME_MAP = {
+  unstable: `unstable_onPluginInit`,
+  stable: `onPluginInit`,
+}

packages/gatsby-source-wordpress/src/gatsby-node.ts

@@ -1,8 +1,25 @@
 import { runApisInSteps } from "./utils/run-steps"
 import * as steps from "./steps"
+import { INITIALIZE_PLUGIN_LIFECYCLE_NAME_MAP } from "./constants"
+
+let coreSupportsOnPluginInit: `unstable` | `stable` | undefined
+
+try {
+  const { isGatsbyNodeLifecycleSupported } = require(`gatsby-plugin-utils`)
+  if (isGatsbyNodeLifecycleSupported(`onPluginInit`)) {
+    coreSupportsOnPluginInit = `stable`
+  } else if (isGatsbyNodeLifecycleSupported(`unstable_onPluginInit`)) {
+    coreSupportsOnPluginInit = `unstable`
+  }
+} catch (e) {
+  console.error(`Could not check if Gatsby supports onPluginInit lifecycle`)
+}
+
+const initializePluginLifeCycleName: string =
+  INITIALIZE_PLUGIN_LIFECYCLE_NAME_MAP[coreSupportsOnPluginInit] || `onPreInit`
 
 module.exports = runApisInSteps({
-  onPreInit: [
+  [initializePluginLifeCycleName]: [
     steps.setGatsbyApiToState,
     steps.setErrorMap,
     steps.tempPreventMultipleInstances,