Return a `Word64` from `loadRegionBaseOffset`

[langston-barrett]

This function returns an (unbounded) Integer:

macaw/base/src/Data/Macaw/Memory/LoadCommon.hs

Line 41 in 0a704c2

loadRegionBaseOffset :: LoadOptions -> Integer

but it does so by converting a Word64:

macaw/base/src/Data/Macaw/Memory/LoadCommon.hs

Line 31 in 0a704c2

LoadOptions { loadOffset :: Maybe Word64

which itself needs to be converted back to a Word64 to be used with functions like memSegment. It should instead return what it's got, namely, a Word64.

This would be a breaking change.