Runner.Service enhancement

[k82cn]

Motivation

Currently, Runner.Service is only has one configuration about stateful. But there're more use cases, e.g. single instances.

Function Specification

Add more parameters to Runner.Service:

• stateful: bool: if the service is stateful, it will persist the common data back to flame-cache. It'll replace RunnerServiceKind.
• autoscale: bool: if the service is autoscale, the Flame will create instance according to the pending tasks; otherwise, only one single instance will be create.

If they're not set, the following default value will be used:

• function: stateful = false, autoscale = true
• class: stateful = false, autoscale = false
• object: stateful = false, autoscale = false

Solutions

1. Add min/max instance for Session
2. In runpy.py, load execution object in on_session_enter.

Additional context

N/A