Use well-typed errors

[JarvisCraft]

Problem

Currently, enum Error is just a bunch of typed Strings which has the cons of:

• Being hard to use it in granular manner;
• Requiring allocations per each string which may never be used.

There also is a problem of not using the std::error::Error::source() infra.

Solution

Replace this with a well-typed error using thiserror for declarative definition.

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PS: self-assigning the issue as I am already working on it.