feat(testing): add Moleculer testing helpers

[Treasure520520]

Summary

Implements the testing helpers proposed in moleculerjs/rfcs#3 and the $100 IssueHunt bounty:

• adds Testing.createBroker() for quiet test brokers with test defaults
• adds Testing.EventCatcher to record emitted/broadcast events and wait for matching events
• adds Testing.MockingCalls to mock dependent broker.call calls and inspect call history
• supports registering local mock services through mockServices
• exports Testing from CommonJS, ESM, and TypeScript declarations

Bounty reference: https://oss.issuehunt.io/r/moleculerjs/rfcs/issues/3
Related RFC: moleculerjs/rfcs#3

Verification

• npx jest test/unit/testing.spec.js --runInBand
• npx jest test/unit/testing.spec.js test/unit/service-broker.spec.js test/unit/middleware.spec.js --runInBand --coverage=false
• npx eslint index.js index.mjs src/testing/*.js test/unit/testing.spec.js
• npx prettier --check index.js index.mjs index.d.ts src/testing/*.js src/testing/*.d.ts test/unit/testing.spec.js
• npm run tsd

Note: npx tsc --noEmit --pretty false currently fails on existing Node 22 typings for crypto.createCipher/createDecipher in src/middlewares/transmit/encryption.js; this PR does not touch that code path.

[Treasure520520]

Codacy is green and there are no open review comments. This PR is ready for maintainer review from my side.

Bounty reference: IssueHunt issue #1304.

[icebob-ai]

Closing this PR. There are multiple duplicate PRs implementing the same RFC #3, and we'll be handling the testing helpers implementation internally as part of the v0.15 release. Thank you for your interest in contributing to Moleculer.