Reorder the `MethodType` enum values so that `METHOD_NONE` is placed last instead of first,
and correspondingly move the `METHOD_NONE` case in the interpreter's dispatch switch to the
end of the case list. This places the most frequently executed method types (`METHOD_PRIMITIVE`,
`METHOD_FOREIGN`, `METHOD_BLOCK`, `METHOD_CTOR`) earlier in both the enum and the switch,
which can improve branch prediction and instruction cache locality in the hot dispatch loop.
When a class is defined, its superclass is not known until runtime since class definitions are imperative statements. This adds a new wrenBindMethod function that walks the bytecode of a method after it is bound to a class, adjusting LOAD_FIELD/STORE_FIELD indices to account for inherited fields and patching superclass dispatch targets. The newClass function now correctly accumulates numFields from the superclass chain, and the VM calls wrenBindMethod when binding methods to a class. Includes new test files for inherited field access and the is operator.
Add closure objects that wrap functions with captured upvalues, enabling
first-class closures that close over local variables from enclosing scopes.
Introduce new bytecode instructions (CODE_CLOSURE, CODE_LOAD_UPVALUE,
CODE_STORE_UPVALUE, CODE_CLOSE_UPVALUE, CODE_RETURN) and a CompilerUpvalue
tracking system with a MAX_UPVALUES limit of 256. Refactor the grammar to
strictly separate statements from expressions, fixing a bug where block
expressions incorrectly popped locals while temporaries remained on the
stack. Rename internal functions (wrenCallFunction, wrenDebugDumpInstruction,
wrenDebugDumpStack) and add Upvalue allocation, closure creation, and
debug dump support for the new instructions.
