lib: smf: Add State Machine Framework

Add an application agnostic State Machine Framework library to
Zephyr that provides an easy way for developers to integrate
state machines into their application.

Twister passed:
twister -T tests/lib/smf/

Signed-off-by: Sam Hurst <[email protected]>

Author: sambhurst

CODEOWNERS

@@ -541,6 +541,7 @@
 /include/toolchain/                       @dcpleung @nashif @andyross
 /include/zephyr.h                         @dcpleung @nashif @andyross
 /kernel/                                  @dcpleung @nashif @andyross
+/lib/smf/                                 @sambhurst
 /lib/util/                                @carlescufi @jakub-uC
 /lib/util/fnmatch/                        @carlescufi @jakub-uC
 /lib/util/getopt/                         @jakub-uC

doc/guides/index.rst

@@ -24,6 +24,7 @@ User and Developer Guides
    platformio/index.rst
    portability/index.rst
    porting/index
+   smf/index.rst
    test/index
    tfm/index
    west/index