Simulations: make polars dependancy optional #97

Job	Run time
Rust lints (libp2p)	2m 57s
Rust lints (waku)	5m 14s
Check (libp2p)	3m 7s
Check (waku)	6m 0s
Test Suite (libp2p, ubuntu-latest)	11m 20s
Test Suite (libp2p, windows-latest)	16m 35s
Test Suite (libp2p, macos-latest)	15m 11s
Test Suite (waku, ubuntu-latest)	13m 13s
Test Suite (waku, windows-latest)	18m 32s
Test Suite (waku, macos-latest)	18m 18s
	1h 50m 27s

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