fix: correctly handle value of initialPromise for fetchWhenDepsChange conditions in useLoadData

[NielsJPeschel]

Proposed changes

On initial load, when passing dependencies into useLoadData that are immediately ready (presumably because they were cached or were never asynchronous in nature), we proceed to try and immediately invoke fetchData, and therefore have initialPromise defined. If initialPromise is in fact a promise, we await it's resolution inside of loadData, and provide the result into the state.

However, in the situation where we desire to re-invoke fetchData to account for updated dependencies (when fetchWhenDepsChange is true in the config), initialPromise is still defined, and bypasses any proceeding fetchData calls.

This PR introduces a fix to this scenario, where we unset initialPromise whenever we enter fetchWhenDepsChange flows.

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