[TIMOB-28061] TiAPI: Add OS version major/minor integer constants

*Summary:* Currently, you can only fetch the OS version as a string via the [Ti.Platform.version](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.Platform-property-version) property. This is not convenient to use when you only want to call APIs on higher OS versions. For example, we've seen a lot of code that looks like the below.

if (OS_IOS && parseInt(Ti.Platform.version.split('.')[0]) >= 13) {
	// Do something on iOS 13 or higher...
}

*Feature Proposal:* Add the following properties to Ti.Platform... * Ti.Platform.versionMajor // Returns an integer. * Ti.Platform.versionMinor // Returns an integer. Also add the following global constants. _(These will pair well with [OS_ANDROID](https://docs.appcelerator.com/platform/latest/#!/api/Global-property-OS_ANDROID) and [OS_IOS](https://docs.appcelerator.com/platform/latest/#!/api/Global-property-OS_IOS).)_ * OS_VERSION_MAJOR * OS_VERSION_MINOR This will make the above code example look simpler like this...

if (OS_IOS && (OS_VERSION_MAJOR >= 13)) {
	// Do something on iOS 13 or higher...
}

*Note:* On Android, we have a [Ti.Platform.Android.API_LEVEL](https://docs.appcelerator.com/platform/latest/#!/api/Titanium.Platform.Android-property-API_LEVEL) constant which is a single integer used to represent all Android OS versions. It's best to use this if you can, but note that no other platform has a similar concept... while all operating system support a <major>.<minor> version that we can use for parity. https://developer.android.com/guide/topics/manifest/uses-sdk-element#ApiLevels