Move block rate and log limit into toml config

[ferglor]

https://smartcontract-it.atlassian.net/browse/AUTO-10027

In this PR, we are:

• Specifying defaults for the automation block rate and log limit in the toml config, based on the existing hard coded values here
• Cleaning up the old hard coded defaults
• Updating the oc2 config types in code to supply these new values

The configuration values are as follows:

Block rate

• For arbitrum we specify a block rate of 4
• For all other supported chains, we specify a block rate of 1

Log limit

• For eth we specify a log limit of 20
• For optimism, BSC, polygon, avax, and base we specify a log limit of 5
• For all other supported chains, we specify a log limit of 2

Open questions

• Not sure if all the chains I've added defaults for are still supported - is there a list of currently supported chains?