Simulations: make polars dependancy optional #92

Job	Run time
Rust lints (libp2p)	2m 55s
Rust lints (waku)	4m 28s
Check (libp2p)	2m 35s
Check (waku)	4m 18s
Test Suite (libp2p, ubuntu-latest)	10m 42s
Test Suite (libp2p, windows-latest)	23m 31s
Test Suite (libp2p, macos-latest)	15m 15s
Test Suite (waku, ubuntu-latest)	19m 46s
Test Suite (waku, windows-latest)	26m 25s
Test Suite (waku, macos-latest)	19m 47s
	2h 9m 42s

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