feat(RouteDiagram): Proper visualisation of parallel processing of the multicast

[mmelko]

Also I added tests for the multicast rendering and did small variables refactor.

Route visualisation without parallelProcessing=true:

with parallelProcessing=true:

[tadayosi]

@mmelko Don't forget to point to the issue that the pull req is supposed to fix from here.

No worries. It's a SO issue :-p

[github-actions]

Test Results

  8 files  ±0    8 suites  ±0   36m 36s ⏱️ +2s
 66 tests ±0   64 ✅ ±0   2 💤 ±0  0 ❌ ±0 
470 runs  ±0  445 ✅  - 1  25 💤 +1  0 ❌ ±0 

Results for commit abdaaee. ± Comparison against base commit e6a61a1.

[hawtio-ci]

Test results

Run attempt: 1999
Detailed summary

NAME	TESTS	PASSED ✅	SKIPPED 💤	FAILED ❌	ERRORS 🚫	TIME 🕖
results-quarkus-node(18)-java(17)-firefox	67	64	3	0	0	317.078
results-quarkus-node(18)-java(21)-firefox	1	1	0	0	0	7.076
results-quarkus-node(20)-java(17)-firefox	67	64	3	0	0	308.876
results-quarkus-node(20)-java(21)-firefox	67	64	3	0	0	311.383
results-springboot-node(18)-java(17)-firefox	67	63	4	0	0	311.961
results-springboot-node(18)-java(21)-firefox	67	63	4	0	0	318.173
results-springboot-node(20)-java(17)-firefox	67	63	4	0	0	310.152
results-springboot-node(20)-java(21)-firefox	67	63	4	0	0	312.237