Implement primitive type narrowing for global functions

Add some very primitive type narrowing for global functions.

General syntax:

if type(doSomething) = "roFunction" then
    doSomething()
end if

You must wrap your function with an if statement that includes one or both of these conditions, but must contain no other conditions. Like this:

if type(theThing) = "roFunction"
if type(theThing) = "Function"
if type(theThing) = "roFunction"  or type(theThing) = "Function"

The order may also be swapped. Like this:

if type(theThing) = "roFunction"
if "roFunction" = type(theThing)

The way we will implement this in v0 is:

• when we're about to add the cannot find name diagnostic, we will walk up the ast tree looking at every if statement. if it matches one of the syntaxes above, then we will NOT add the diagnostic.

NOTE: this is NOT a broad type guard implementation, and is exclusively for global functions

Start at the code path that adds the "cannot find name" diagnostic and inspect the AST traversal around enclosing if statements. Implement only the listed type(...) condition forms for global functions, then verify that matching conditions suppress the diagnostic while other conditions still report it.