fix: implement AdaptUnmarshalParams

[JordiParraCrespo]

Description

This pull request introduces a compatibility adapter for EVM parameters, allowing the system to seamlessly handle both the current cosmos.evm schema and the legacy Ethermint schema. The main change is the addition of a robust unmarshalling function, which is now used by the keeper to read parameters, ensuring smooth upgrades and backward compatibility. Comprehensive tests are added to verify correct behavior across all supported scenarios.

Core compatibility improvements:

• Added AdaptUnmarshalParams in x/vm/keeper/adapter.go to transparently unmarshal EVM params from either the current or legacy schema, converting fields as needed and handling schema incompatibilities.
• Updated Keeper.GetParams in x/vm/keeper/params.go to use AdaptUnmarshalParams, ensuring that parameter reads work regardless of the underlying schema, and panic on unrecoverable errors.

Testing and validation:

• Added x/vm/keeper/adapter_test.go with unit tests covering current schema, legacy schema, minimal legacy params, invalid legacy values, and random bytes, ensuring the adapter behaves correctly in all edge cases.
• Added x/vm/keeper/params_test.go with integration-style tests for GetParams, verifying correct operation with empty stores, both schemas, and error handling for invalid data.

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