Update USUAL ! operator to attempt type cast

[joshua-azyra]

Background

It is possible to implicitly cast a USUAL to a LOGIC value but not possible to apply the not (!) operator.
This seems counter intuitive as in one case the USUAL can be treated as though it is a LOGIC but not in the other case.

I think it would feel more consistent to attempt to implicitly cast the

Example

Both giving

Details

The change to the runtime should make no impact on performance for the happy path (unchanged so there should be no overhead with casting)
It will allow USUAL of type [] to be treated a LOGIC
It will change the exception for the other USUAL types

I'm happy for this PR to be closed without merging if you think the current behaviour is preferable.

[cpyrgas]

Guys, this is incompatible to VO though. Actually VO does not allow casting a usual holding an it to a logic at all. All attempts below to make such an assignment, result to a data type runtime error in VO. Not sure why we did allow the USUAL(INT)->LOGIC conversion in X# in the first place, but does not look correct. Maybe it was for compatibility with vulcan?

LOCAL u AS USUAL
LOCAL l AS LOGIC
LOCAL cb AS CODEBLOCK
cb := {||999}
IF FALSE//Eval(cb) // runtime error in VO
   ? "aaaa"
ENDIF
u := 1
l := u  // runtime error
l := Eval(cb)  // runtime error

[cpyrgas]

Only way to assign an INT (or an INT in a USUAL) to LOGIC in VO, is with a strong cast. A soft conversion also fails:

LOCAL u AS USUAL
LOCAL l AS LOGIC
LOCAL n AS INT

n := 123
l := LOGIC(_CAST,n) // works in VO
? l // TRUE
u := 1
l := LOGIC(_CAST,u) // works in VO
? l // TRUE
l := LOGIC(u) // error
? l

So I think it's better to handle this in the explicit conversion operator from usual to logic instead.