This commit uses the new .. zephyr:code-sample-category directive to
categorize code samples across the tree.
Updates existing legacy references to manually defined targets to now
use :zephyr:code-sample-category: role instead.
Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
This commit moves the C++ samples under `samples/subsys/cpp` to
`samples/cpp` because the C++ language and standard library support is
not a "subsystem" (aka. API) in conventional sense and the samples
demonstrating them should belong directly under the top samples
directory as does POSIX support.
Signed-off-by: Stephanos Ioannidis <stephanos.ioannidis@nordicsemi.no>