EVM Node: The RPC mode does not rely on the observer config anymore

The only remaining usage of the observer config by the RPC mode is to get a EVM node endpoint to connect to. Instead, we compute an EVM endpoint based on the rpc_port and rpc_addr config value.

The current proposal will assume http:// as the scheme to connect to the read-write node, which is consistent with every deployment we have from partners. Besides, it is compatible with what I’m calling “catch-all bind addresses” in both IPv4 and IPv6. When these are used as bind address, we replace rpc_addr with localhost as the way to connect to the read-write node.

Manually testing the MR

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR