[android] Replace Oboe audio with SDL3 audio (#4338)

Supersedes #4335.

Replaces the Oboe audio backend with SDL3, since we already support it.
A few caveats:

- SDL defines a JVM OnLoad method already, so we have to instead hijack
  NativeLibrary for id_cache initialization
- This also means some internal fields in Double/Integer/Boolean (namely
  `value`) can't be accessed, so I switched those to methods for now.
- SDL Java sources are pulled in from the CI package.
- Since we can't use SDLActivity, `SDL.setupJNI()` handles everything

Signed-off-by: crueter <[email protected]>

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
- [x] I have read and followed the [AI Policy](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/AI.md)
- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

-------------------

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4338
Reviewed-by: Lizzie and Samuel <[email protected]>
Reviewed-by: MaranBr <[email protected]>

.gitignore

@@ -63,3 +63,6 @@ artifacts
 /install*
 vulkansdk*.exe
 *.tar.zst
+
+# Build-time generated external sources
+externals/generated