Json pretty encoder doesn't encode enums the same way as the normal encoder

[drasich]

Encoding an enum field with the pretty encoder results in an ExpectedError when decoding.

In emit_enum_variant of the pretty encoder,
"variants" and "fields" need to be added to behave the same way as the normal encoder.

[kmcallister]

Do you have a simple test case?

[bkoropoff]

Taking a look

[alexcrichton]

Closed by #17623

[drasich]

Thank you for fixing this!