Add custom plan modifier for groups field in the MQ User resource

[turkenf]

Description

Introduced a custom plan modifier (listSortModifier) to ensure the groups attribute in the MQ User resource is always sorted alphabetically during the plan phase.
This modifier sorts the groups list and prevents unnecessary diffs between plan and state.

Fixes crossplane-contrib/provider-upjet-aws#1657

[github-actions]

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[turkenf]

Closed in favor of #284