[memprof] Compute CallStackId when deserializing IndexedAllocationInfo (#86421)

There are two ways to create in-memory instances of
IndexedAllocationInfo -- deserialization of the raw MemProf data and
that of the indexed MemProf data.

With:

  commit 74799f42
  Author: Kazu Hirata <kazu@google.com>
  Date:   Sat Mar 23 19:50:15 2024 -0700

we compute CallStackId for each call stack in IndexedAllocationInfo
while deserializing the raw MemProf data.

This patch does the same while deserilizing the indexed MemProf data.

As with the patch above, this patch does not add any use of
CallStackId yet.