chore(tests): restructure & cleanup

[danisharora099]

This PR:

• renames NimGoNode to ServiceNode
• restructures folders & files into lib and utils

Notes

• generally a good cleanup of the package for readability
• Important for feat: SDK for redundant usage of filter/lightpush #1463 as we need to introduce a way/an API to check multiple nodes (creating a wrapper over ServiceNode and MessageCollector): feat: lightpush & filter send requests to multiple peers #1779

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
Waku core	82.06 KB (0%)	1.7 s (0%)	2 s (-25.05% 🔽)	3.6 s
Waku Simple Light Node	265.66 KB (0%)	5.4 s (0%)	4.3 s (+56.12% 🔺)	9.6 s
ECIES encryption	31.97 KB (0%)	640 ms (0%)	1.2 s (-5.3% 🔽)	1.9 s
Symmetric encryption	31.96 KB (0%)	640 ms (0%)	789 ms (-23.97% 🔽)	1.5 s
DNS discovery	123.17 KB (0%)	2.5 s (0%)	1.8 s (-11.95% 🔽)	4.2 s
Privacy preserving protocols	119.37 KB (0%)	2.4 s (0%)	1.8 s (-21.7% 🔽)	4.2 s
Light protocols	79.5 KB (0%)	1.6 s (0%)	1.8 s (-5.28% 🔽)	3.4 s
History retrieval protocols	78.39 KB (0%)	1.6 s (0%)	1.2 s (-6.57% 🔽)	2.8 s
Deterministic Message Hashing	5.92 KB (0%)	119 ms (0%)	433 ms (-3.67% 🔽)	551 ms