Add to the ImHashMap ref state arguments to be propagated into the Update delegates

Pros:

- The idea is that we pass the struct state deep into the stack when updating (other ops) on Map
- We may get the result back using this stack, like the old value, some calculated value, etc.
- Encourage the passing state, by enabling more scenarios where you can pass it, and avoid memory allocation and performance hit introducing closure in delegate.
- Have the fewer overloads because passing the struct parameter by ref enables to combine multiple state items into one without hurting performance.