AlignAssignmentStatement overhaul to fix issues and include handing of Enums.

[liamjpeters]

PR Summary

Overhauls the AlignAssignmentStatement rule to include handling of enums as well as fix several issues with Hashtable alignment.

I am very open to feedback and suggestions 😀.

Setting defaults have changed. Previously the rule could be enabled, but not do anything, as CheckHashtable (previously the only setting and gating all functionality) defaulted to $false. I've changed this (as well as the new settings) to default to $true. If you enable the rule - it will do something now. You can then optionally disable any parts you don't want. The rule is opt-in and there are already breaking changes in this PR (see the baby and the bath water below). Docs update shows and explains new settings.

Hashtable alignment issues resolved include:

• Erroring when the key of a key-value pair is an expression containing an equals sign

  @{
      ($Key1 = 5) = "Value1"
      Key2 = "Value2"
  }

  Invoke-ScriptAnalyzer: Start position cannot be before End position.

  This is because of the way the current implementation finds Equals tokens. It find the equals token within the expression.

  It results in a correction extent that has an end column which is before the start column.

• Erasing inline comments when they appear between the key of the key-value pair and the Equals token.

  @{
      Key1 <#Sneakycomment#> = "Value1"
      Key2 = "Value2"
  }

  results in

  @{
      Key1 = "Value1"
      Key2 = "Value2"
  }

• Performance scaling poorly. This is due to how Equals tokens of Key-Value pairs are located. For each Key-Value pair the list of tokens is scanned (from the beginning) until the relevant Equals token is found. This means that, as a worst case, performance scales quadratically - proportional to half the number of Key-Value pairs in the file * the number of tokens.

  We can improve this by scanning the tokens once and keeping track of all the Equals tokens and what line they appear on. This reduces complexity to essentially linear time with negligible memory use. Goes from O(H*T) -> O(H+T).

  I've put together some stress-test files (one saved as a gist here and script to generate them here) and ran only the AlignAssignmentStatement rule on them. Results below from my machine, averaged over 5 runs (with the first cold run discarded):

  	Violations	Pre-PR	Post-PR
  100 Hashtables with 100 KVP	8,301	3.627s	0.221s
  500 Hashtables with 100 KVP	41,124	121.902s	1.533s
  1000 Hashtables with 100 KVP	82,147	457.873s	2.165s

• The baby is thrown out with the bath water. If a single Key-Value pair is not in the expected format (Key and Equals-sign on same line, no two kvp on same line etc) the whole hashtable is skipped. I don't think this should be the case. The rule should consider and align the keys which are in the expected format and ignore the others. The rule is opt-in and so people using it want alignment - we should do our best to provide it.

I've done my best to expand the test coverage.

Fixes #1739
Fixes #1860

Would address downstream VSCode Extension issue: PowerShell/vscode-powershell#5138

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.