move contexts from openbeta-graphql to sandbag

[musoke]

Comments in openbeta-graphql say that grade contexts should be defined in sandbag. https://github.com/OpenBeta/openbeta-graphql/blob/dab9388193d4733e577c454a31354245253fdced/src/GradeUtils.ts#L5-L85

This is required for open-tacos to benefit from the those definitions.

Wait until in progress changes have settled and versions are synchronized.

Depends on:

• [ ] https://github.com/OpenBeta/openbeta-graphql/pull/283
• [ ] https://github.com/OpenBeta/openbeta-graphql/pull/252
• [ ] https://github.com/OpenBeta/openbeta-graphql/pull/269
• [ ] https://github.com/OpenBeta/openbeta-graphql/pull/268
• [ ] https://github.com/OpenBeta/sandbag/issues/125