Ambiguous error tracker

[mkatychev]

Sticky issue to track all ambiguous/unhelpful errors, add more as comments

Please keep comments for sub-issues in this format:

• <ambiguous error> for <action>

  $ wkg <subcommand> [...<flags>]
  Error: <primary error message>
  
  Caused by:
      0: <unhelpful error chain>

Errors

• interface not found for fetch

  $ wkg fetch --config .wkg/config.toml
  Error: failed to fetch dependencies for wit
  
  Caused by:
      0: failed to merge package from directory `wit`
      1: interface not found in package