Append record stub generated code

Instead of prepending (old behavior)
Some cleanup
Fix comments
Fix comments #2
Fix interactive code issue
Making the happy path work
Making the unhappy path work

* simplify tests
Simplify code
Polishing
Catch exn
Simplify & remove dead code
Fix bug with with record fields on the same line
Guards against possible exceptions
Better code gen with patterns on the same line
Normalize FCS range in tryFindTokenLPosInRange
Reduce smart tagger pressure on CPU
Merge pull request #481 from OkayX6/append-union-pattern-match-case

Append record stub & union pattern match case