Get Scripted Functions Metadata from AST

Use AST::iter_functions to iterate through all the script-defined functions in an AST.

`ScriptFnMetadata`

The type returned from the iterator is ScriptFnMetadata with the following fields:

Field	Requires	Type	Description
`name`		`&str`	Name of function
`params`		`Vec<&str>`	Number of parameters
`access`		`FnAccess`	• `FnAccess::Public` (public) • `FnAccess::Private` (`private`)
`comments`	`metadata`	`Vec<&str>`	Doc-comments, if any, one per line