update(userspace/engine): introduce new rule_reader class

The rule_reader class is responsible of parsing the YAML ruleset text and of using the rule_loader
to store the new definition in the internal state. This is a first step towards separating the YAML
reading logic from the rule parsing one. Potentially, this will allow us to read rulesets from another
YAML library or from something different than YAML files too.

Signed-off-by: Jason Dellaluce <jasondellaluce@gmail.com>

userspace/engine/CMakeLists.txt

@@ -19,6 +19,7 @@ set(FALCO_ENGINE_SOURCE_FILES
     formats.cpp
     filter_macro_resolver.cpp
     rule_loader.cpp
+    rule_reader.cpp
     stats_manager.cpp)
 
 add_library(falco_engine STATIC ${FALCO_ENGINE_SOURCE_FILES})