[interpreter] Add support for scalable operands.

test/cctest/interpreter/bytecode_expectations/Throw.golden

 #
 # Autogenerated by generate-bytecode-expectations.
 #
 
 ---
 pool type: string
 execute: yes
 wrap: yes
 
 ---
 snippet: "
   throw 1;
 "
 frame size: 0
 parameter count: 1
 bytecode array length: 4
 bytecodes: [
   B(StackCheck),
-  B(LdaSmi8), U8(1),
+  B(LdaSmi), U8(1),
   B(Throw),
 ]
 constant pool: [
 ]
 handlers: [
 ]
 
 ---
 snippet: "
   throw 'Error';
@@ skipping 14 matching lines @@
 
 ---
 snippet: "
   var a = 1; if (a) { throw 'Error'; };
 "
 frame size: 1
 parameter count: 1
 bytecode array length: 12
 bytecodes: [
   B(StackCheck),
-  B(LdaSmi8), U8(1),
+  B(LdaSmi), U8(1),
   B(Star), R(0),
   B(JumpIfToBooleanFalse), U8(5),
   B(LdaConstant), U8(0),
   B(Throw),
   B(LdaUndefined),
   B(Return),
 ]
 constant pool: [
   "Error",
 ]
 handlers: [
 ]