refator(backend-common): extract test utilities to plugin api

Signed-off-by: Camila Belo <camilaibs@gmail.com>

plugins/techdocs-node/src/stages/publish/local.test.ts

@@ -17,7 +17,7 @@ import {
   getVoidLogger,
   PluginEndpointDiscovery,
 } from '@backstage/backend-common';
-import { overridePackagePathResolution } from '@backstage/backend-common/testUtils';
+import { overridePackagePathResolution } from '@backstage/backend-plugin-api/testUtils';
 import { ConfigReader } from '@backstage/config';
 import express from 'express';
 import request from 'supertest';