aws lambda - relayer observer

[eugypalu]

Resolves #1527

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 new behavior?

This Lambda automates the process of maintaining relayer balances, ensuring they always have sufficient funds to operate

1. Balance monitoring: Periodically checks the ETH balance of the main relayer account and individual relayers.

2. Automatic funding: If a relayer's balance falls below a predefined threshold, the Lambda attempts to fund it automatically with a fixed amount of ETH.

3. Slack notifications: Sends alerts to Slack channel #relayers-observer when:

   • The main relayer account balance is low and requires replenishment.
   • An error occurs while attempting to fund a relayer.

4. Uses AWS Secrets Manager to securely retrieve the private keys necessary for transactions.

5. Manual replenishment of the main account: avoid automating the withdraw call to the coinbase address to replenish the main relayer account. This decision was taken to prevent the need for an automatic call by the contract owner within the Lambda, thus maintaining greater control over significant fund replenishment operations.

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This change is 

[Eikix]

Can you add AWS CDK Python probably it is the best idea

[ClementWalter]

why do we need to exclude them all?

[eugypalu]

in my opinion should be excluded, these are the the lint issues:

- Ensure that HEALTHCHECK instructions have been added to container images
- Ensure that a user for the container has been created
- Specify version with `yum install -y <package>-<version>`
- Pin versions in pip. Instead of `pip install <package>` use `pip install <package>==<version>`
- Specify at least 1 USER command in Dockerfile with non-root user as argument

[Eikix]

What is the status of this @eugypalu