Return ExtrinsicDetails alongside decoded static extrinsics

[tadeohepperle]

fixes #1359

We introduce a new wrapper type around a static extrinsic of typeE that contains details about the extrinsic (e.g. signature, signed extensions, original bytes, metadata...)

pub struct FoundExtrinsic<T: Client, C, E> {
    pub details: ExtrinsicDetails,
    pub value: E
}

[jsdw]

This looks awesome!

I'm surprised no book/examples needed changing; something to look at quickly maybe just to see that the example docs etc still make sense (clearly none were actually using the decoded extrinsic since no errors), but can be done separately!

[tadeohepperle]

I'm surprised no book/examples needed changing

Not anymore! Since I just merged the PR with the additional examples to master, this PR now also needed an adjustment :)

[jsdw]

Nice!