Make Opus support opt-in

[freya022]

Pull Request Etiquette

• I have checked the PRs for upcoming features/bug fixes.
• I have read the contributing guidelines.

Changes

• Internal code
• Library interface (affecting end-user code)
• Documentation
• Other: README, build logic

Closes Issue: NaN

Description

This PR moves the Opus encoder and decoder to a separate module, as well as the opus-java and JNA dependencies with it.

This makes the Opus codec opt-in, as it was previously opt-out; and eliminates the no-opus artifact.

Future work may include:

• Updating libopus (1.1 -> 1.5.2), see Build Opus from source, update Gradle and publishing logic discord-java/opus-java#13
• Setting the encoder's bitrate to the channel's
• Creating an additional module using Java 22's Foreign Function Interface, to eliminate the need for JNA bindings and the overhead it brings
• Allowing users to change encoder settings globally/per connection, such as:
  • Setting the application type when creating an encoder
  • Enabling in-band forward error correction
  • Setting the encoder's computational complexity

This also fixes the min artifact not excluding the "additional audio" dependencies