Use cmake targets

Description

• Use cmake targets instead of separate usage of libraries/includes. This allows fro a much cleaner approach to the use of dependencies, allows for flag incorporation into the targets, etc.
• Add some minimal versions for ROOT, Openloops, etc.

Test Plan

Compilation should pass.

Additional Checklist Items

• I have updated documentation as needed No action needed.
• I considered if this should be cherry-picked/ported somewhere else (rel-2-x or master), and if yes, opened a corresponding issue or MR No action needed.

cmake/Modules/FindRivet.cmake

@@ -97,13 +97,12 @@ if (RIVET_VERSION VERSION_GREATER_EQUAL 4.0.0)
     set(RIVET4 1)
     set(RIVET_YODA_MIN_VERSION "2.0.0")
     set(RIVET_HEPMC3_MIN_VERSION "3.2.6")    
-    set(RIVET_MKHTML_ARGS "--mc-errs")
-
+    set(RIVET_MKHTML_ARGS "")
 else()
     set(RIVET4 0)
     set(RIVET_YODA_MIN_VERSION "1.8.0")
     set(RIVET_HEPMC3_MIN_VERSION "3.2.3")
-    set(RIVET_MKHTML_ARGS "")
+    set(RIVET_MKHTML_ARGS "--mc-errs")
 endif()
 message(STATUS "SHERPA: WARNING: YODA with RIVET_YODA_MIN_VERSION=${RIVET_YODA_MIN_VERSION} will be requested by Rivet.")
 find_package(YODA ${RIVET_YODA_MIN_VERSION} REQUIRED)