refactor: combine all error variants into `web_prover_core::error::WebProverError`

[Autoparallel]

Tasks

• Take all variants of errors from the three crates and combine them into a single enum in the web-prover-core crate.
• Refactor to use this.

What can we do while we're here to support #511 ?

[piotr-roslaniec]

I thought about this today, and I'm not convinced that moving all errors to core is a panacea for our problems (not sure what these are, anyway). If we can move some of the shared error types to core that would be great, but IMHO errors that are specific to the notary (or other domains) should rest in their respective crates.

@Autoparallel I just sprinkled some comments on the existing error types setup: https://github.com/pluto/web-prover/compare/feat/manifest-v2...feat/refactor-errors%23556?expand=1

[Autoparallel]

I don't think it is a problem either. Just a code cleanliness suggestion. Perhaps it doesn't make complete sense if there are also specific errors that the notary can make.