While in theory RNA collections of IDs will have unique names in common
use cases, it can happen that there are naming collisions (due to a same
RNA collection having ID pointers to data from different libraries,
having the same name).
This situation is deadly for liboverride applying code, since it rely on
finding which item of the collection to modify by using its name.
To alleviate the problem, this commit changes the way items are searched
for, by adding an extra first check to find an item which matches both
the requested name and index.
While not perfect, this should reduce the breaking cases when production
files get dirty and start having complex mangling of override and linked
data naming.
a05419f18b