feat: store_byte memory method

[enitrat]

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build-related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Resolves: #325

What is the new behavior?

• Adds a store_byte method to memory for MSTORE8 opcode
• Fixes total gas accounting in python script.

Does this introduce a breaking change?

• Yes
• No

[github-actions]

Snapshot Comparison Report:

�[92mIMPROVEMENTS�[0m
�[92mevm::tests::test_instructions::test_memory_operations::test_exec_mstore8_should_store_last_uint8_offset_31 635534 --> 462222 | -27.27 %�[0m
�[92mevm::tests::test_instructions::test_memory_operations::test_exec_mstore8_should_store_last_uint8_offset_63 928364 --> 755052 | -18.67 %�[0m
�[92mevm::tests::test_instructions::test_memory_operations::test_exec_mstore8_should_store_uint8_offset_31 635534 --> 462222 | -27.27 %�[0m
�[92mevm::tests::test_instructions::test_memory_operations::test_exec_mstore8_should_store_uint8_offset_31_then_uint8_offset_30 1022258 --> 867314 | -15.16 %�[0m

�[91mWORSENED�[0m
�[91mevm::tests::test_instructions::test_memory_operations::test_exec_mstore8_should_store_uint8_offset_30 635534 --> 653902 2.89 %�[0m
�[92mOverall gas change: performance improvement, gas consumption-0.24 %�[0m

[ClementWalter]

see comments

[enitrat]

Addressed comments

[Eikix]

looks good to me overall

[Eikix]

lgtm

approved after changes