Function logging support

[RobertIndie]

Motivation

It's an important need to support logging for the function. We need these logs to check if the function is working correctly, and in case of failure, help identify the problem.

Goals

• Support logging in the wasm function
• Support accessing logs from the function-stream

Implementation

API Changes

• We could use the stderr stream to get logs from the wasm function
• Add new rest endpoints for function-stream: /api/v1/function/{function_name}/logs. This will return all the logs from the function

Notes

We need to support accessing the logs while the function is executing.