Add Uint512Serializer for Cairo uint512 type support

[Copilot]

This PR implements the missing Uint512Serializer to support serialization and deserialization of 512-bit unsigned integers in Cairo contracts.

Implementation

The Uint512Serializer follows the same architectural pattern as the existing Uint256Serializer but extends support to 512-bit values. A uint512 is represented in Cairo as a structure with four uint128 components:

{limb0: Uint128, limb1: Uint128, limb2: Uint128, limb3: Uint128}

Key Features

• Dual Input Support: Accepts both integer values and structured dictionaries
• Comprehensive Validation: Range checking for all components and overall value
• Error Handling: Clear error messages for invalid inputs and out-of-range values
• Mathematical Correctness: Proper bit layout where value = limb3×2^384 + limb2×2^256 + limb1×2^128 + limb0

Usage Examples

from starknet_py.serialization.data_serializers import Uint512Serializer

serializer = Uint512Serializer()

# Serialize integer values
serializer.serialize(123)  # [123, 0, 0, 0]
serializer.serialize(2**128)  # [0, 1, 0, 0]

# Serialize dictionary input
serializer.serialize({
    'limb0': 123, 'limb1': 456, 
    'limb2': 789, 'limb3': 101
})  # [123, 456, 789, 101]

# Deserialize back to integer
serializer.deserialize([123, 456, 789, 101])  # Returns the original uint512 value

Files Added/Modified

• Added: starknet_py/serialization/data_serializers/uint512_serializer.py - Main implementation
• Added: starknet_py/tests/unit/serialization/data_serializers/uint512_serializer_test.py - Comprehensive tests
• Modified: starknet_py/cairo/felt.py - Added uint512_range_check function
• Modified: starknet_py/serialization/data_serializers/__init__.py - Export new serializer

Testing

The implementation includes comprehensive tests covering:

• Valid value serialization/deserialization
• Invalid value rejection with proper error messages
• Type validation for incorrect input types
• Edge cases including maximum values and boundary conditions
• Round-trip verification for data integrity

All tests follow the same patterns as existing serializer tests to maintain consistency.

Fixes #1639.

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[franciszekjob]

General comment: instead of having keys low0, low1, high0 and high1, we should use lib0, ..., limb3. As reference, please take a look at u512 docs in Cairo:
https://docs.cairo-lang.org/core/tmp/core-integer-u512.html

[Copilot]

General comment: instead of having keys low0, low1, high0 and high1, we should use lib0, ..., limb3. As reference, please take a look at u512 docs in Cairo:
https://docs.cairo-lang.org/core/tmp/core-...

Updated the Uint512Serializer to use limb0, limb1, limb2, limb3 keys instead of low0, low1, high0, high1 to align with the Cairo u512 documentation. All tests pass with the new naming convention. Commit: e0c6751