fix: add Ethereum address checksum validation tool

[crStiv]

Implemented Features:

• New Go tool in ops/cmd/check_addresses that finds and fixes incorrectly checksummed Ethereum addresses
• Added CI check to prevent merging files with incorrect address formats
• Tool can check specific files, all TOML files, or just the standard-versions-sepolia.toml
• Fails with exit code 1 when bad addresses are found (for CI integration)

Background:

Issue #938 pointed out that non-checksummed addresses cause problems when importing into Solidity. So I guess my fix can help with solving the issue.

Testing Done:

I've tested this by manually invalidating addresses and confirming the tool catches and fixes them correctly. Added docs explaining usage and command flags.

Screenshots:

1. Start of the process
   
2. The tool finding an incorrect address
   
3. Fixing it with the -fix flag
   
4. Verifying all addresses now pass validation