Thrust: Make the maximum input size depend on the amount of available device memory in the `fallback_allocator` example to ensure a fallback occurs.
Thrust: Make the maximum input size depend on the amount of available device memory in the `fallback_allocator` example to ensure a fallback occurs.

[git-p4: depot-paths = "//sw/gpgpu/thrust/": change = 23040967]

jaredhoberock/thrust,thrust/thrust,andrewcorrigan/thrust-multi-permutation-iterator,jaredhoberock/thrust,thrust/thrust,andrewcorrigan/thrust-multi-permutation-iterator,andrewcorrigan/thrust-multi-permutation-iterator,thrust/thrust,jaredhoberock/thrust,jaredhoberock/thrust,jaredhoberock/thrust,thrust/thrust,thrust/thrust