Fix deprecation upgrade code for speech credentials

[compulim]

Fixes #2822.

Changelog Entry

Fixed

• Fixes #2822. Fixed credentials should return authorizationToken and subscriptionKey as string and allow empty LUIS reference grammar ID, by @compulim in PR #2824

Description

The change introduced in #2759 has a deprecation upgrade code. But the deprecation upgrade code was broken.

The deprecation upgrade code should turns authorization token and subscription key, into the format of credentials = async () => ({ authorizationToken: '...', region: 'westus2' }) (or subscriptionKey).

The deprecation upgrade code should handle these types of authorization token and subscription key:

• String
• Promise that resolves into a string
• Function that returns a string
• Promise function that returns a string

This PR also update to use .eslintignore.

Specific Changes

• Updated createCognitiveServicesSpeechServicesPonyfillFactory.js
  • For deprecation upgrade, build the credentials so that it will return a () => Promise<{ authorizationToken: string, region: string }>
  • If LUIS reference grammar ID is not supplied, it will send an empty array, instead of luis/undefined-PRODUCTION
• Added .eslintignore

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• Testing Added

[corinagum]

LGTM