Improve Error Messages and Remove Unknown Errors

[charlespierce]

Tracking the progress of improving the error messages to make them more user-friendly and helpful.

Tasks

• Audit existing error messages to improve helpfulness #295 Audit existing error messages to improve helpfulness (PR: Finish auditing the existing error messages #336)
• Update calls to .unknown() in distro module #296 Update calls to .unknown in distro module (PR: Rework remaining errors #344)
• Update calls to .unknown() in event module #297 Update calls to .unknown in event module (PR: Rework unknown errors in event module #337)
• Update calls to .unknown() in fs module #298 Update calls to .unknown in fs module (PR: Rework remaining errors #344)
• Update calls to .unknown() in hook module #299 Update calls to .unknown in hook module (PR: Rework remaining errors #344)
• Update calls to .unknown() in inventory module #300 Update calls to .unknown in inventory module (PR: Rework remaining errors #344)
• Update calls to .unknown() in manifest module #301 Update calls to .unknown in manifest module (PR: Rework unknown errors in manifest module #342)
• Update calls to .unknown() in platform module #302 Update calls to .unknown in platform module (PR: Rework unknown errors in platform module #338)
• Update calls to .unknown() in project module #303 Update calls to .unknown in project module (PR: Rework unknown errors in project module #339)
• Update calls to .unknown() in shell module #304 Update calls to .unknown in shell module (PR: Rework unknown errors in shell module #340)
• Update calls to .unknown() in toolchain module #305 Update calls to .unknown in toolchain module (PR: Rework remaining errors #344)
• Use a constant for common CTAs in ErrorDetails #343 Move common CTAs into constants (PR: Rework remaining errors #344)
• Remove .unknown() helper method #306 Remove .unknown() helper
• Use a friendly error instead of unimplemented! macro #359 Remove unimplemented! and other macros that cause a panic (PR: Replace unimplemented macro with ErrorDetails variant #399)

Notes

The process for updating a call to .unknown() is (as described in #249):

1. Add a new entry to the ErrorDetails enum, including information you need for the error message if necessary.
2. Update the match block in the impl Display for ErrorDetails block to include the error message for the new error.
3. Update the match block in the impl NotionFail for ErrorDetails block to return the correct ExitCode for the new error.
4. Replace any .unknown() calls that should wrap an failure in the new error with a .with_context(|error| ErrorDetails::NewError) call, setting any contextual values needed.