Add resolvable checks implementation

[romanodanilo]

Description

Addressing #15 #18, implement relative checks, test data and test code

How was the PR tested?

1. Unit-test with sample data. All unit tests passed.

Notes
example output
entity

 <Issue issueId="0" description="Issue flagging when an entity is referred in a entityRef attribute but it is not declared among Entities" level="1" ruleUID="asam.net:xosc:1.2.0:reference_control.resolvable_entity_references">
        <Locations description="Entity at /OpenSCENARIO/Storyboard/Init/Actions/Private with id Vehicle 2 not found among defined Entities ">
          <XMLLocation xpath="/OpenSCENARIO/Storyboard/Init/Actions/Private"/>
        </Locations>
      </Issue>

variable

<Issue issueId="1" description="Issue flagging when a variable is referred in a variableRef attribute but it is not found within ScenarioDefinition" level="1" ruleUID="asam.net:xosc:1.2.0:reference_control.resolvable_variable_reference">
        <Locations description="Variable with id unknownReferenceForYPosition not found within ScenarioDefinition">
          <XMLLocation xpath="/OpenSCENARIO/Storyboard/Init/Actions/GlobalAction/VariableAction[3]"/>
        </Locations>
      </Issue>
      <Issue issueId="2" description="Issue flagging when a variable is referred in a variableRef attribute but it is not found within ScenarioDefinition" level="1" ruleUID="asam.net:xosc:1.2.0:reference_control.resolvable_variable_reference">
        <Locations description="Variable with id foo not found within ScenarioDefinition">
          <XMLLocation xpath="/OpenSCENARIO/Storyboard/Init/Actions/GlobalAction/VariableAction[4]"/>
        </Locations>
      </Issue>

[hoangtungdinh]

Thanks @romanodanilo