Move InnerProductTypes out of base to proof_primitive

[stuarttimwhite]

Background and Motivation

NOTE: https://github.com/spaceandtimelabs/sxt-proof-of-sql/issues/230 should be completed before this ticket can be done. Additionally, be aware that some of the code changes for this issue are likely to conflict with the code changes in the following issue: https://github.com/spaceandtimelabs/sxt-proof-of-sql/issues/234

Currently, we have reference to 3 types that we want removed from proof-of-sql/src/base:

1. Curve25519Scalar
2. RistrettoPoint
3. InnerProductProof

Any references to these types should be moved to the proof_primitive directory in its own directory named "inner_product". Ultimately, we are trying to remove all cyclic dependencies caused by these types.

Changes Required

Each of these should be a separate PR.

• [ ] Move Curve25519Scalar and its unit tests to new directory proof_primitive/inner_product.
• [ ] Move RistrettoPoint and its unit tests to inner_product.
• [ ] Move InnerProductProof and its unit tests to inner_product.
• [ ] If there is any reference to any of these types remaining (most likely within a test), either move those to inner_product or replace with one of TestScalar, NaiveCommitment, or TestEvaluationProof.