[REFACTOR] Add init API for runtime

[yunwei37]

Is your feature request related to a problem? Please describe.

The General Runtime init need to do several things:

• init config
• Setup sig handlers
• init global memory

Describe the solution you'd like

We need a clear API design of how the user can use it as a general runtime. Init is part of it.

Describe alternatives you've considered

Provide usage examples

Additional context