fix: update full_chain_test.py to follow full_chain_odd.py (#3956)

* support `--output-obj` like #3180. Can also still use `-cc` to output all formats.
* Fuse initial and final sim particles when `--edm4hep` input specified (sync with #3804)

Next, we should remove the command-line options for `full_chain_odd.py`.

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
	- Introduced a new `--output-obj` argument for enabling object file output.

- **Improvements**
	- Updated help text for the `--output-csv` argument to clarify output options.
	- Enhanced output directory handling to support multiple output formats.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Examples/Scripts/Python/full_chain_test.py

@@ -81,7 +81,12 @@ def parse_args():
         "--output-csv",
         action="count",
         default=0,
-        help="Use CSV output instead of ROOT. Specify -cc to output both.",
+        help="Use CSV output instead of ROOT. Specify -cc to output all formats (ROOT, CSV, and obj).",
+    )
+    parser.add_argument(
+        "--output-obj",
+        action="store_true",
+        help="Enable obj output",
     )
     parser.add_argument(
         "-n",
@@ -272,6 +277,11 @@ def full_chain(args):
     outputDirCsv = outputDir if args.output_csv != 0 else None
     outputDirLessCsv = outputDirLess if args.output_csv != 0 else None
     outputDirMoreCsv = outputDirMore if args.output_csv != 0 else None
+    outputDirObj = (
+        outputDirLess
+        if args.output_obj
+        else outputDir if args.output_csv == 2 else None
+    )
 
     # fmt: off
     if args.generic_detector:
@@ -392,8 +402,7 @@ def full_chain(args):
                 "LongStripEndcapReadout",
             ],
             outputParticlesGenerator="particles_input",
-            outputParticlesInitial="particles_initial",
-            outputParticlesFinal="particles_final",
+            outputParticlesSimulation="particles_simulated",
             outputSimHits="simhits",
             graphvizOutput="graphviz",
             dd4hepDetector=detector,
@@ -483,6 +492,7 @@ def full_chain(args):
                 postSelectParticles=postSelectParticles,
                 outputDirRoot=outputDirRoot,
                 outputDirCsv=outputDirCsv,
+                outputDirObj=outputDirObj,
             )
         else:
             if s.config.numThreads != 1:
@@ -508,6 +518,7 @@ def full_chain(args):
                 killAfterTime=25 * u.ns,
                 outputDirRoot=outputDirRoot,
                 outputDirCsv=outputDirCsv,
+                outputDirObj=outputDirObj,
             )
 
     addDigitization(