[FEA] Have a global pinned memory pool by default about cudf HOT 2 OPEN

Measured memory use by hostdevice_vector in cuIO benchmarks as a percentage of peak device memory use. The pinned memory use is proportional to device memory use, so we can use the peak device memory use as a measure of how much pinned memory we would need if we used up all device memory.
The results show that we would never fall back to new pinned allocations with a pinned pool sized at 4% of device memory capacity. However, even at 0.5%, the pool can be used to allocate 90% of used pinned memory without additional allocations.

from cudf.

Benchmarking results:

"relative throughput" is the average ratio of the throughput with the custom resource and the throughput with default (pinned, non-pooled) resource.

Benchmarks consistently show improvement with pooled resource compared to pinned allocations.
read_json shows disproportionate improvement because of small benchmarks that are hugely impacted by a single pinned allocation.
Data also show that small pools bring very similar performance improvement to the pool that never falls back to new allocations.
Surprisingly, benchmarks also show that using pageable memory in hostdevice_vector is preferable to pinned (non-pooled).

TODO: run benchmarks from #15585 because we expect to see higher impact in multi-threaded use cases.

from cudf.