Add Long-Running Envelope Worker Isolate for Android, iOS, macOS

[buenaflor]

Description

Summary

Create a single long-lived Dart isolate to process Sentry envelopes -> offloads sending envelopes from the main isolate

Requirements

• FFI / JNI is already used for captureEnvelope
• Auto-spawn on init
• Message transfer via TransferrableTypedData

Notes

• Need to benchmark to make sure the performance gain is still worth it for small envelopes - if sending small envelopes in the main isolate is still faster then we'll only use the isolate for envelopes bigger than a certain size

[linear]

DART-198 Add Long-Running Envelope Worker Isolate for Android, iOS, macOS