[roll] Roll fuchsia [kernel] Fix zx_info_task_stats_t for restricted aspaces

This change fixes a bug in how we compute zx_info_task_stats_t for
processes with restricted aspaces.  The bug arrose because of an
impdenance mismatch between ProcessDispatcher::GetStats and
VmAspace::GetMemoryUsage.  GetStats reports numbers using
process-centric definitions of shared and private while GetMemoryUsage
computes values using aspace-centric definitions of shared and
private.

Prior to this change, ProcessDispatcher::GetStats simply summed
results of GetMemoryUsage on its two aspaces.

Now, it transforms the aspace-centric numbers into process-centric
numbers using the ShareableProcessState's count.  See fxbug.dev/123525
and the linked doc for more details.

Note, even after this change there is still an accuracy issue with
mem_scaled_shared_bytes.  While the values will now "sum to 1",
process that share aspaces will have a smaller
"fractional-responsibility" than processes that do not share aspaces.
For example, imagine there is only one page on the system and three
processes, P1, P2, and P3.  P1 and P2 each have their own restricted
aspace as well as normal aspace they share with each other (count is
2).  P3 has no restricted aspace and its normal aspace has a count of
1.  The page is mapped into P1/P2's normal (shared) aspace and P3's
aspace.  Ideally, the mem_scaled_shared_bytes for each of these
processes should be 1/3 of a page.  However, as of this CL, P1 and
P2's mem_scaled_shared_bytes will be 1/4 of a page each and p3's will
be 1/2 of a page.

Add new test case to verify zx_info_task_stats_t for shared processes.

Test: fx test fuchsia-pkg://fuchsia.com/process-test
Original-Fixed: 123525
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/819103
Original-Revision: 4222783b9390b5e805ffee79549561a37a93d5db
GitOrigin-RevId: 31b3bbfc68f7995710c34facafb371beae2618e6
Change-Id: I70d1f33dce80a2d7452a14ba26e5ce1c6dff7f68