Summary:
Depends on D3910.
Adds shared scriptspb proto definitions.
These will be used both by the compiler and by the scriptmgr in the cloud so they need to be in shared.

Test Plan: N/A

Reviewers: #engineering, philkuz

Reviewed By: #engineering, philkuz

Differential Revision: https://phab.c.pixielabs.ai/D3916

GitOrigin-RevId: 86ddf3f35847e0141bc15d830d7a2fcfb6360eee