[Core] Introduce type for resource dictionaries

[pcmoritz]

Description

I'm not sure if there is currently a way to do this, ideally resource dictionaries would be typed like

class Resources(TypedDict, extra_items=float):
    CPU: float
    GPU: float
    memory: float
    object_store_memory: float

I don't think this is currently possible (please let us know if you know it is) -- but will be possible with this PEP: https://peps.python.org/pep-0728/

Use case

This will give people autocomplete in their IDE and make it less likely to mistype the keys in the dict (and still be fully compatible with the current API) :)

[rynewang]

Context: #48709