use API to validate user-supplied kernel buffers

[zephyrbot]

Reported by Andrew Boie:

Many system calls will work on user-provided buffers. We need to have a way to prove that these buffers reside in a region of memory that a thread has read or write access to. We will need to define a general interface for this (probably calling into architecture-specific APIs), and then add conditionally compiled hooks into it in all our kernel APIs which work on buffers.

Separate JIRAs have been filed to implement this on ARM and x86. Scope of this JIRA is to modify the system calls themselves to use this API.

(Imported from Jira ZEP-2192)