Add new MissingTryBlock rule

[iRon7]

PR Summary

Although #2098 didn't get an up-for-graps label, I did create the suggested Add new MissingTryBlock rule to warn when catch or finally blocks are not preceded by a try block because:

• I think that a catch block that misses a try block is less valid than a try block that misses a catch block which causes an parse error by the engine
  • and therefore even deserves the severity Error
• A missing try block might easily get unnoticed during design time but will very likely fail during runtime
• It happened twice now that someone in our company tried to publish a script that was missing a try block

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Change is not breaking
• Make sure all .cs, .ps1 and .psm1 files have the correct copyright header
• Make sure you've added a new test if existing tests do not effectively test the code changed and/or updated documentation
• This PR is ready to merge and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: to the beginning of the title and remove the prefix when the PR is ready.