added extra metadata for macos/android and setvoice fix

[hioshih]

Greetings!

This is my first PR, so please let me know if I made some mistake.

• macOS: I added some of the voice metadata that was already available for iOS to macOS.
• macOS and iOS: I fixed a situation that I detected on macOS but could occur in iOS in the future, where if a voice has multiple quality versions it was unpredictable which version would be used. Now it will either get the highest quality available, or allow the voice to be set using a map with an 'identifier'.
• Android: I added some metadata that might potentially be interesting (quality, latency, network_required and features). Also, made a function to deal once with metadata retrieval from getDefaultVoice and getVoices, to avoid duplicated code.

As an example, here is some metadata from a Samsung device, that has some interesting extra information:

//samsung engine
{features: bixbyVoice=true  variant=l03 aiVoice=true    version=312472000   versionName=3.1.24.72   deeplink=samsungapps://productDetail/com.samsung.SMT.lang_en_us_l03 packageName=com.samsung.SMT.lang_en_us_l03  name=Voz 1  gender=female   uid=null, latency: normal, name: en-US-SMTl03, locale: eng-x-lvariant-l03, network_required: 0, quality: very high}

//google engine
{features: networkTimeoutMs notInstalled    legacySetLanguageVoice  networkRetriesCount, latency: low, name: en-GB-language, locale: en-GB, network_required: 0, quality: high}

[dlutton]

@hioshih thanks for this PR, do you mind updating the README and then I'll merge it in.