Add new function which checks for the proper version of dotnet

[JamesWTruher]

This will improve the experience when the wrong version of dotnet is present by creating an error very early on in the process with a better error message

Now the developer will see something similar to the following:

PS /users/james/src/github/forks/JamesWTruher/PSScriptAnalyzer> ./build
Incorrect dotnet version: have '2.1.403' need '2.2.102'
At /users/james/src/github/forks/JamesWTruher/PSScriptAnalyzer/build.psm1:137 char:9
         throw 'Incorrect dotnet version: have '' need ' ...
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 CategoryInfo          : OperationStopped: (Incorrect dotne... need '2.2.102':String) [], RuntimeException
 FullyQualifiedErrorId : Incorrect dotnet version: have '2.1.403' need '2.2.102'

PR Summary

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.

[bergmeister]

We need this to work on the WMF4 build as well (it doesn't at the moment) and we should also remove/move existing code here that is used for CI to avoid duplication. There is a lot of handling for major/minor version, why not use the --list-sdks option instead to avoid handling those scenarios and also to not make it fail and just install the exact required version? In terms of handling the error and minor/major versions, I think dotnet build does that already together with global.json, so we should rather try to just rather try to propagate this error from the layering between build.ps1 and build.psm1 to the user.

[JamesWTruher]

i'm closing this and will incorporate it into #1139