variant errors on top-level errors mask real error

When using say a restricted error variant, throwing an unsupported error will be masked by the "invalid variant" error in the bindings.

In componentize bindings, we should specially handle invalid error variants at the top-level to be able to provide better debugging output.

Start by tracing the componentize bindings path that handles restricted error variants, focusing on how an unsupported top-level error becomes an invalid-variant error. Reproduce the masking behavior and compare the available error information. Done means the original unsupported error remains visible in the debugging output instead of being masked.

Written by the indexing model from the issue text.