Update error messages in Should -Throw

[fflaten]

PR Summary

Enhances Should -Throw assertion with:

• Improved filter-summary in error message
  • Specifically using word like for message-filter to hint at the use of -like operator.
    Related discussion ExpectedMessage comparison fails #1793
• Removes duplicate helper-functions covered by Format.ps1
• Fixes error when ActualValue is missing or not a scriptblock.
  Missing BEFORE
  
  Non-scriptblock BEFORE (conversion error = printed whole function)
  
  Missing or Non-scriptblock AFTER
  

Fix #2064

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• Tests are added/update (if required)
• Documentation is updated/added (if required)