Add simple CLI to fetch and archive C-Chain blocks

[aaronbuchwald]

Why this should be merged

How this works

How this was tested

Need to be documented in RELEASES.md?

[aaronbuchwald]

Failing CI due to TestMustNotImport when it tries to import customethclient to fetch blocks correctly from the public API:

[aaronbuchwald]

Thinking that we should add the following triggers to CI:

PR - create a local network with N (100) blocks, fetch the blocks, and test we can iterate over them successfully
manual workflow - fetch blocks from provided RPC URL, optionally start with existing DB pulled from S3, configure GH timeout, and post to new location in S3
cronjob - maintain an S3 object that contains all of the blocks up to tip and update it once a month