User friendly output on the command line - second cut

[azriel91]

Part two of use friendly CLI output (part one -- #28).

• Refactor Error to consolidate all State*Deserialize and Serialize errors into a single variant.

• Specify diagnostic source code, spans, and help messages for each variant.

• Update *Cmds and tests to write errors to OutputWrite -- maybe not? Depends if the Cmd is meant to be the one writing.

• Update InMemoryTextOutput for the web to display miette reports.

• Update book documentation on how to use miette.

  The download example uses a workaround to show inner diagnostics to get around the pass-though not working issue:

  • Render inner diagnostics zkat/miette#170
  • Wrapping other Errors without losing diagnostics zkat/miette#172

[azriel91]

Closing -- specific issues should be opened with well-defined scope for each task.

The above tasks are infinitely growing.