ElementSegmentValidator

Validator of ElementSegment nodes.

From the docs:

• The table C.tables[x] must be defined in the context.
• Let limits elemtype be the table type C.tables[x].
• The element type elemtype must be funcref.
• The expression expr must be valid with result type [i32].
• The expression expr must be constant.
• For each y_i in y*, the function C.funcs[y] must be defined in the context.
• Then the element segment is valid.