Deprecate detail::available_device_memory, most detail/aligned.hpp utilities, and optional pool_memory_resource initial size

[harrism]

Description

Follow-on to #1417, this PR deprecates the following:

• rmm::detail::available_device_memory in favor of rmm::available_device_memory
• rmm::detail::is_aligned, rmm::detail::align_up and related alignment utility functions in favor of the rmm:: top level namespace versions.
• The rmm::pool_memory_resource constructors that take an optional initial size parameter.

Should be merged after the following:

• Provide explicit pool sizes and avoid RMM detail APIs cugraph#4086
• Provide explicit pool size and avoid RMM detail APIs cudf#14741
• Provide explicit pool size for pool_memory_resources and clean up includes raft#2088

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[harrism]

/merge