fix: update hashing function to latest spec

[jamesondh]

Motivation

The DR hashing function incorrectly includes payback_address and seda_payload, which are not known by external chains at time of DR creation.

Explanation of Changes

• Removed payback_address and seda_payload from DR hashing function
• Refactored memo hash to remove value, keeping only chain_id and nonce. This is only to reflect how memo is calculated in the EVM contracts, i.e. the CosmWasm contracts don't care about how memo is calculated.
• Removed deprecated util functions hash_update() and pad_to_32_bytes() since the hashing function no longer requires them

Testing

• Created a new test test_hash_data_request() to isolate the DR hashing function and to mirror an identical test on the EVM repo, see: https://github.com/sedaprotocol/seda-evm-contracts/blob/20fffd45abcdcd16e27c4f8ef0a4c343e0dbc371/test/SedaOracle.t.sol#L110

Currently with the test inputs, the CosmWasm contracts and EVM contracts generate a test DR hash of 0x27e7eec2f319302826ea53ae08b4aac6c4824cc07eafcdaf740501b3d603d0aa.

Related PRs and Issues

Related to sedaprotocol/seda-evm-contracts#13
Created new issue #65 because Hash (dr_binary_id and tally_binary_id) are currently Strings instead of fixed size byte arrays. Also requires the same update on the EVM side.