feat: preserve class abi

[kariy]

the abi field in rpc format for the contract class can be an arbitrary string. this is what the jsonrps spec says:

   "abi": {
            "title": "ABI",
            "type": "string",
            "description": "The class ABI, as supplied by the user declaring the class"
          }

currently, if the rpc abi string can't be converted into the ContractAbi type, it will fail during the deserialization phase. the abi string must be preserved as well because it's part of the class hash computation. so we need to preserve the raw string even if it's just some random string.

Starknet class with arbitrary abi string: 0x22b7d06d355ddb1c485ec9cc09b488e77e63318db8833104aed56d598416417 where the abi string returned by the RPC is literally this "Declared from starknet-rs test case. Timestamp (ms): 1709974545243".

superseded #353 .

this change also include a database version bump ( 7 -> 8 ) because of the change made to the value type of the Classes table i.e., the katana_primitives::class::ContractClass enum.

[codecov]

Codecov Report

❌ Patch coverage is 78.43137% with 44 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.96%. Comparing base (9bde0ae) to head (5a0549d).
⚠️ Report is 183 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/primitives/src/class.rs	70.00%	15 Missing ⚠️
...rates/storage/db/src/models/versioned/class/mod.rs	50.00%	15 Missing ⚠️
crates/rpc/rpc-types/src/class.rs	94.00%	6 Missing ⚠️
crates/storage/db/src/models/versioned/class/v7.rs	0.00%	6 Missing ⚠️
...rage/provider/provider/src/providers/fork/state.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #356      +/-   ##
==========================================
+ Coverage   73.32%   74.96%   +1.64%     
==========================================
  Files         209      250      +41     
  Lines       23132    30234    +7102     
==========================================
+ Hits        16961    22666    +5705     
- Misses       6171     7568    +1397     

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