refactor: move ProofType into raiko_lib

[keroro520]

The ProofType is a primitive component within Raiko. However, currently, there is some redundancy and confusion with similar items. I intend to refactor ProofType for clarity and independence as follows:

1. Move ProofType to raiko_lib, to ensure that ProofType be indenpendent with other items

2. Merge Proof System ID into ProofType, to eliminate redundant definitions and simplify the management of proof types for taskdb

   • Proof System ID, also known as "prover code"
   • Proof System ID RISC0_PROVER_CODE = 3
   • Proof System ID SP1_PROVER_CODE = 1

3. Merge VerifierType into ProofType.

   • VerifierType

This pull request focuses on the first step: moving ProofType into raiko_lib and making it independent of other constructs. In fact, this pull request is more easy than it looks like, and it doesn't introduce any new changes:

• fe5d48a moves the ProofType definition into raiko-lib
• 33c88d9 adjust some relevant code