The previous implementation used GetRawOperand(), which allows a nicely
unified handling of all scalar types, but returns an unsigned type.
Because of this, generate-bytecode-expectations couldn't properly handle
negative numbers.

This commit differentiate between different types of scalar operands and
uses the appropriate getter from i::interpreter::BytecodeArrayIterator,
thus correctly handling signed types where needed.

Two new helpers have been added to i::interpreter::Bytecodes:

 * IsImmediateOperandType()
 * IsIndexOperandType()

with the intuitive semantic.

BUG=v8:4280
LOG=N

Review URL: https://codereview.chromium.org/1684113002

Cr-Commit-Position: refs/heads/master@{#33874}