Non-functional code fix improvements

[psfinaki]

• Changing option to voption in the internal interface to reduce allocations
• Using FSharpRangeToTextSpan instead of TryFSharpRangeToTextSpan - this has been inconsistent so far and I cannot see this throwing in the code fix context. If it does throw - it should be tested and fixed on the code fix level
• Fixing a typo in a file name
• Splitting some code