Support for granular storage slot override

[kawahwookiee]

Rationale

Since a storage slot is 32 bytes or 256 bits in size, it can fit several smaller variables. If one needed to perform an eth_call with an override of a single variable in a slot, they would need to request the contents of the slot, change the target segment, and use the current full-slot override. With the proposed feature, the request step could be avoided.

Implementation

This issue is accompanied by the PR 32874

[s1na]

Closing based on discussion here: #32874 (comment)