zombienet: use another collator image for the slashing test (#1386)

* zombienet: use test-parachain image for the slashing test

* use the right image

* try polkadot-parachain image

* try naming collator alice 



* add needed job for the pipeline

* fix user id in polkadot-parachain-debug image

* small tweaks to the test

* another small tweak

* yet another small tweak

* bump zombienet version

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Co-authored-by: Javier Viola <javier@parity.io>