Add timeout option to uri requests

[ctedgar]

Hi @ryanheise,

This is a pull request to address #1119, it includes the following changes:

1. just_audio_platform_interface: Updated the implementations of UriAudioSourceMessage to include the optional timeoutMillis parameter.
2. just_audio:

• Added timeout parameters to UriAudioSource and StreamAudioSource implementations.
• Updated AudioPlayer.java to expect the optional timeout parameter and respect it if set.
• Added a test case under 'load error' to simulate the timeout error and to also validate the plumbing of the new parameter. (i.e. assert that the timeout property is making it down to the platform message)

I realize there may be a need to implement the same functionality for all other platforms. I've just carried out the changes for Android as it's what I could test comfortably.

I added change notes and bumped the versions both just_audio and just_audio_platform_interface though I suppose just_audio_platform_interface would need to be published first followed by just_audio, if these changes are accepted ofcourse.

Note for local testing: Update just_audio_platform_interface/just_audio_web dependency in just_audio pubspec to point to local folder

Regards,
Cris

[ctedgar]

Had not accounted LockCachingAudioSource and the URI proxied requests, so added similar timeout overrides LockCaching requests and for proxied requests.

Regards,
Cris