Propose high level design thoughts for plugin sandboxing

[saratvemulapalli]

Is your feature request related to a problem? Please describe.
As we start on to think about the problem: https://github.com/saratvemulapalli/OpenSearch/blob/feature/sandboxing/sandboxing-design.md#problem

Propose high level design ideas, pros and cons for each in the design doc.

Meta issue: #1422

[saratvemulapalli]

Started updating the design in the meta issue.
Closing this.