Improve operator-help returned from Get-ShouldOperator

[fflaten]

PR Summary

This PR introduces customized help format for assertion operators. It displays:

• Name
• Aliases (if any)
• Syntax
• Synopsis
• Examples

Also cleans up examples in assertions help and fixes broken Should-Throw help.

Before

After

Fix #1163

PR Checklist

• PR has meaningful title
• Summary describes changes
• PR is ready to be merged
  • If not, use the arrow next to Create Pull Request to mark it as a draft. PR can be marked Ready for review when it's ready.
• Tests are added/update (if required)
• Documentation is updated/added (if required)

[nohwnd]

@fflaten is this ready to be merged?

[fflaten]

If the output looks right, then I'm good with merging 👍 Haven't tested the format at PS3.0 yet, but should work.