Make the `ethereum-tracker` example application work

[MathieuDutSik]

Motivation

The oracle have been implemented but we did not test it. This is now done.

Proposal

The following was done:

• The FetchJson was taking just the URL and now is taking url/payload.
• The ethereum-tracker smart contract was introduced.
• The end-to-end test is introduced.

Some additional improvements to ethereum features and use statements are possible.

Test Plan

One additional test has been added which is the point of the PR.

Release Plan

We are starting to have Ethereum developing, so we will need to put some documentation for it.

Links

• reviewer checklist

[afck]

(To fix the tests you'll need to apply cargo insta.)

[afck]

In the title, did you mean to write this?

Make the ethereum-tracker example application work

[MathieuDutSik]

In the title, did you mean to write this?

Make the ethereum-tracker example application work

Ok, renamed.

[afck]

@MathieuDutSik: Did you add a comment somewhere, why this specific revision is needed?

alloy = { git = "https://github.com/alloy-rs/alloy", rev = "b79db21734cffddc11753fe62ba571565c896f42", default-features = false }