clean up symbol error reporting

[zerbina]

Summary

• don't report "cannot call" error when using symbol of routines
  where the definition has an error
• don't report "only identifier found is an error" when using let/
  var/const symbol where the initializer expression has an error
• these errors don't provide any additional information and only
  clutter compiler and nimsuggest output

Details

• use a common erroneous symbol handling path in semSym
• don't turn skLet, skVar, and skConst into skErrors when the
  definition AST has an error
• use the silent adWrappedSymError diagnostic for erroneous callees
• remove the CalleeHasAnError diagnostic and report
• add tests to make sure the new error reporting behaviour works
• adjust the tpointerprocs.nim, which is affected by the different
  error reporting

[saem]

adWrappedSymError is so much better, really wish this approach occurred to me when I was working on this.

[saem]

/merge

[github-actions]

Merge requested by: @saem

Contents after the first section break of the PR description has been removed and preserved below:

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Notes for Reviewers

• builds upon sem: fix crash due to incorrect error handling #1372