Add verbose mode

[tatomyr]

Is your feature request related to a problem? Please describe.

Redocly CLI shows nice error messages for handled exceptions. For unhandled exceptions error stacktrace is shown. We can also show a nice error message in Terminal for this kind of exceptions and show the stacktrace only with --verbose option.

Describe the solution you'd like

Add --verbose flag to all commands and show error details only if it is provided.

Describe alternatives you've considered

Doing nothing. Current approach is very much ok.

[simon-spinner]

If an exception is thrown inside a custom plugin (rule or decorator), you see the error message but not the stack trace on the console. It is hard to figure out which rule or decorator broke and where exactly. It would be great if --verbose would also print out the stack traces. Maybe I am missing something, but I always start the debugger to figure out where the error happens, which is cumbersome.