Implement state handling for Retracted status

[Niederb]

• Move Retracted enum value from UnexpectedTxStatus to XtStatus
• Provide is_final method for TransactionStatus
  • Currently not used, but I think it makes sense to provide it
• Return from watch method as soon as a final state is reached
• Provide separate method to populate events for an ExtrinsicReport
  • I think separating it makes sense but I'm not sure we want to add it to the trait
  • See also Refactor SubmitAndWatch trait #773

[haerdib]

I'm not sure about the distribution and function name. We do a lot here:

• Events from the node are fetched
• Events are checked if they contain errors and if so, return an Error
• Copy the events into the report.

So the function name does only describe one of three important points.

How about the following: Let the ExtrinsicReport implement the function is_success or similar, as well as the function add_events for easy event adding. This would not bloat the trait event more and still offer most of the convenience. Caveat: The events still need to be fetched separately. Not sure if it should part of the ExtrinsicReport struct, as this involves chain interaction.

E.g. it could look like something like this:

let mut report = self
			.submit_and_watch_opaque_extrinsic_until_without_events(encoded_extrinsic, watch_until)
			.await?;
if watch_until < XtStatus::InBlock {
			return Ok(report)
		}
let block_hash = report.block_hash.ok_or(Error::BlockHashNotFound)?;
let extrinsic_events =
	self.fetch_events_for_extrinsic(block_hash, report.extrinsic_hash).await?;
report.add_events(extrinsic_events);
report.is_success()?;
return Ok(report);

What do you think?