Bounds checks for values/inputs/outputs (#1572)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/1572

Avoid buffer overruns of the `values_` table by checking indies.

Pre-check that inputs/outputs point to valid values so we can fail non-fatally.

Add unit tests for the testable changes.

Reviewed By: larryliu0820

Differential Revision: D52646899

fbshipit-source-id: b8fe643ae946da9b77ed54687559f75cf9010703