fix: added missing feature flag for multisync

[jarekr-da]

This PR adds EnableMultiSynchronizer flag to localnet bootstrap (app-synchronizer.sc)
(After protocol switch to 35 it is mandatory now)

Also test added - there was already ReassignmentTest - but was not using localnet (that is why the problem was not detected).

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[moritzkiefer-da]

thx looks reasonable to me, you are missing an updateTestConfigForParallelRuns and there is a stray println

[moritzkiefer-da]

you probably don't want a random println here

[jarekr-da]

(oops) removed

[moritzkiefer-da]

you're still missing sbt updateTestConfigForParallelRuns

[moritzkiefer-da]

thanks Jarek!