Rename "release" target to avoid clash with "nx release"

[philrz]

When trying to build the GA Zui v1.4.0 release candidates it became apparent that the move from nx 15.8.7 to 16.10.0 as part of #2834 caused an unexpected problem: Somewhere between those versions they introduced an nx release command that happened to clash with our use of release as a target in Zui's package.json. Once that was understood, the workaround of changing the target name as shown in this PR got me up & running again quickly.

Since we already had release-insiders I opted to call the new target release-zui for symmetry. Then I did similar treatment turning the adjacent package target into package-zui for consistency, plus it insulates us against the possibility that the verb package gets claimed one day by nx as well. 😛