Improve forc-client abi update logic

[kayagokalp]

We should remove the build script if possible, if not we should make sure that it is very robust. One very interesting problem would be related to the comment below:

Since that's a non-greedy capture, it might need to be anchored to the end of the string, otherwise ",\)\); appearing inside the abi source may end the match early:

let re = regex::Regex::new(r#"abigen!\(Contract\(name = "ProxyContract", abi = ".*?",\)\);$"#)

Originally posted by @alfiedotwtf in #6535 (comment)

[kayagokalp]

related to #6527