Fix experiment user recording and "group type" mismatch

Fixes experiment user record_experiment_user and experiment_enabled? "group type" mismatch

• The tracking_group is calculated by record_experiment_user is for current_user subject, whereas the one calculated by the experiment_enabled? is calculated for the cookie subject.
• I will add tests after the proposal make sense

Related to #297379 (closed)

Affected experiments are any experiment doing the below with subject:

experiment_enabled?(:foo)

record_experiment_user(:foo)

Does this MR meet the acceptance criteria?

Conformity

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• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
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