PVF host prechecking support v2 (#4123)

* pvf host: store only compiled artifacts on disk

* Correctly handle failed artifacts

* Serialize result of PVF preparation uniquely

* Set the artifact state depending on the result

* Return the result of PVF preparation directly

* Move PrepareError to the error module

* Update doc comments

* Update misleading comment

* pvf host: turn off parallel compilation

* pvf host: implement precheck requests

* Fix warnings

* Unnecessary clone

* Add a note about timed out outcome

* Revert the pool outcome handling behavior

* Move the prepare result type into error mod

* Test prepare done

* fmt

* Add an explanation to wasmtime config

* Split pvf host test

* Add precheck to dictionary

Co-authored-by: Sergei Shulepov <sergei@parity.io>