doc: posix: aep: condense aep documentation

The POSIX Application Environment Profiles are additive and
offer incrementally more features over the System Interfaces.

For example, PSE51 includes all of the features of the Minimal
Realtime System Profile plus all of the System Interfaces.
PSE52 includes all of the features of the Realtime Controller
System Profile, plus the features of PSE51, plus the System
Interfaces, and so on.

It makes sense to take advantage of that and to condense the
AEP documenation.

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