Define plan_limits trait for each plan

What does this MR do and why?

This MR defines traits for the :plan_limits factory for every plan type:

build(:plan_limits, :default_plan)
build(:plan_limits, :free_plan)
build(:plan_limits, :ultimate_plan)
# ... and so on

This can be done in the FOSS :plan_limits factory because in FOSS this will define only the "default" plan, and in EE this will define all the EE plans. This is the same as how the :plan factory currently works.

More of these traits will be used in !89591 (merged).

MR acceptance checklist

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