[PATCH v12 0/4] support large align and nid in Rust allocators

[Vitaly Wool <vitaly.wool@konsulko.se>]

The coming patches provide the ability for Rust allocators to set
NUMA node and large alignment.

Changelog:
v2 -> v3:
* fixed the build breakage for non-MMU configs
v3 -> v4:
* added NUMA node support for k[v]realloc (patch #2)
* removed extra logic in Rust helpers
* patch for Rust allocators split into 2 (align: patch #3 and
  NUMA ids: patch #4)
v4 -> v5:
* reworked NUMA node support for k[v]realloc for all 3 <alloc>_node
  functions to have the same signature
* all 3 <alloc>_node slab/vmalloc functions now support alignment
  specification
* Rust helpers are extended with new functions, the old ones are left
  intact
* Rust support for NUMA nodes comes first now (as patch #3)
v5 -> v6:
* added <alloc>_node_align functions to keep the existing interfaces
  intact
* clearer separation for Rust support of MUNA ids and large alignments
v6 -> v7:
* NUMA identifier as a new Rust type (NumaNode)
* better documentation for changed and new functions and constants
v7 -> v8:
* removed NumaError
* small cleanups per reviewers' comments
v8 -> v9:
* realloc functions can now reallocate memory for a different NUMA
  node
* better comments/explanations in the Rust part
v9 -> v10:
* refined behavior when memory is being reallocated for a different
  NUMA node, comments added
* cleanups in the Rust part, rustfmt ran
* typos corrected
v10 -> v11:
* added documentation for the NO_NODE constant
* added node parameter to Allocator's alloc/realloc instead of adding
  separate alloc_node resp. realloc_node functions, modified users of
  alloc/realloc in accordance with that
v11 -> v12:
* some redundant _noprof functions removed in patch 2/4
* c'n'p error fixed in patch 2/4 (vmalloc_to_page -> virt_to_page)
* some typo corrections and documentation updates, primarily in patch
  3/4

Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.se>