doc: release: 4.3: deprecate CONFIG_POSIX_API

Add release notes about the deprecation of CONFIG_POSIX_API.

User should instead use one of the pre-defined POSIX subprofiles

CONFIG_POSIX_AEP_CHOICE_BASE
CONFIG_POSIX_AEP_CHOICE_PSE51
CONFIG_POSIX_AEP_CHOICE_PSE52
CONFIG_POSIX_AEP_CHOICE_PSE53

and libraries should depend on CONFIG_POSIX_SYSTEM_INTERFACES as well as
other POSIX Option Groups, as needed.

For more information, please see

https://pubs.opengroup.org/onlinepubs/9799919799/xrat/V4_subprofiles.html

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

Author: cfriedt

doc/releases/release-notes-4.3.rst

@@ -142,6 +142,9 @@ Deprecated APIs and options
 
 * :kconfig:option:`CONFIG_XOPEN_STREAMS` was deprecated. Instead, use :kconfig:option:`CONFIG_XSI_STREAMS`.
 
+* :kconfig:option:`CONFIG_POSIX_API` was deprecated. See :ref:`POSIX Configuration<posix_config>`
+  for more details.
+
 New APIs and options
 ====================