Split ParserState::consume() into two separate methods

[JakeQZ]

• One for the string parameter;
• One for the int parameter.

The caller should know what type they are passing and therefore be able to call the appropriate method.

Making this change would avoid having a mixed-type parameter, which is not great for static analysis.

The class has been marked as @internal since 8.7, so we can freely change the public methods.

But before doing so, we should add a dedicated TestCase for the class.