Add a process manager "class"

In many places there's a need to keep track of sub-processes
spawned by the main process. Such processes need to be looked up
by various parameters and interacted with.

Having a common, reliable and fast implementation with high test
coverage that holds the various pieces of information about
sub-processes together is beneficial.

In the future, we should extend this new API with the process
spawning and termination functionality.

Ticket: CFE-3572
Changelog: None

Author: vpodzime

libutils/Makefile.am

@@ -63,6 +63,7 @@ libutils_la_SOURCES = \
 	platform.h condition_macros.h \
 	printsize.h \
 	proc_keyvalue.c proc_keyvalue.h \
+	proc_manager.c proc_manager.h \
 	queue.c queue.h \
 	rb-tree.c rb-tree.h \
 	refcount.c refcount.h \