fix: explicit nwaku subscriptions in tests

[SionoiS]

Problem

When interop testing with nwaku, tests did not subscribe nwaku to the default pubsub topic. Those tests only worked so far because of the default behavior of nwaku WAS to subscribe to the default pubsub topic and cache messages received on it.

With waku-org/nwaku#1983 this is no longer the case.

Solution

Tests that call "get_waku_v2_relay_v1_messages" must call "post_waku_v2_relay_v1_subscriptions" before hand. Otherwise no messages will be cached.

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
Waku core	28.79 KB (0%)	576 ms (0%)	1.7 s (-8.11% 🔽)	2.3 s
Waku Simple Light Node	310.09 KB (0%)	6.3 s (0%)	5.7 s (+7.56% 🔺)	11.9 s
ECIES encryption	28.68 KB (0%)	574 ms (0%)	1.6 s (+17.13% 🔺)	2.2 s
Symmetric encryption	28.68 KB (0%)	574 ms (0%)	1.6 s (+163.58% 🔺)	2.1 s
DNS discovery	118.59 KB (0%)	2.4 s (0%)	2.8 s (+11.77% 🔺)	5.2 s
Privacy preserving protocols	122.6 KB (0%)	2.5 s (0%)	2.9 s (+17.86% 🔺)	5.4 s
Light protocols	29.25 KB (0%)	585 ms (0%)	1.2 s (-27.35% 🔽)	1.7 s
History retrieval protocols	28.34 KB (0%)	567 ms (0%)	954 ms (-23.67% 🔽)	1.6 s
Deterministic Message Hashing	5.64 KB (0%)	113 ms (0%)	352 ms (-42.89% 🔽)	465 ms

[SionoiS]

One test is failing but it seams unrelated.