Revert "libutilscallstack is private VNDK-SP"

CallStack.cpp was part of libutils, but has been separated into a new
library libutilscallstack [1] and then made invisible to vendors [2].
However, this is causing problem to the vendors who have been using
the CallStack class from libutils, because the class is no longer
available to them.

In order to support them, marking libutilscallstack as
'vendor_available: true'.

This reverts commit a32678df.

[1] https://android-review.googlesource.com/c/platform/system/core/+/591954
[2] https://android-review.googlesource.com/c/platform/system/core/+/599754
Bug: 74600214
Test: m -j
Test: 2016/2017 pixel devices boots to the UI and Photo Editing works

Change-Id: Iaa232ed978378b566a4710e2320ee6ed04572e14