Provide decent error message for wrapped errors

[ivmarkov]

Add an error: Box<dyn std::error::Error> member to the Error enum here. Then include the original error message (and possibly its backtrace, if any) in the Debug and Display impl for the matter-rs Error enum.

Just like the backtrace member, it should be enabled only when both std and backtrace features are enabled, as it would be bringing non-trivial cost to the unhappy path.

Yet very useful for proper diagnostics of errors originating outside of matter-rs itself.