feat/ add base network

[LautaroNavarro]

Before submitting this PR, please make sure:

• Your code builds clean without any errors or warnings
• You are using approved title ("feat/", "fix/", "docs/", "refactor/")

A description of the changes proposed in the pull request:
Add base network, and mainnet + sepolia chains

Tests performed by the developer:

• Tested creating a connection using uniswap connect + network base + chain mainnet
• Tested creating a connection using uniswap connect + network base + chain sepolia
• Tested getting the balance for mainnet wallet
• Tested getting the balance for sepolia wallet
  
  

Tips for QA testing:
To test this with the hummingbot client you will need to add the base network to the native_tokens list in the gateway_config_utils.py file. (Inside of the hummingbot repository, and not the gateway repository)

[LautaroNavarro]

@fengtality can you approve the workflow run?

[fengtality]

@LautaroNavarro I don't think Base should be a separate chain, but rather a Ethereum L2 network, like Arbitrum and Optimism. There's actually a separate Gateway PR for Base support: #329

I'll take a look at your changes and see what I can add

[fengtality]

Closing in favor of #329.

Rationale:

• Base should be added as an Ethereum network, not a new chain
• Base token lists included in this PR are wrong

[LautaroNavarro]

@fengtality thanks! Yes, adding base as an Ethereum network make sense since it's a L2. About the tokens, I'm not really sure where do you get the list from, I went to uniswap and took them from the requests.
Do you have an ETA for #329 ?