config(chat): try opt in implicit @workspace context once if users are in treatment group [WIP]

[Will-ShaoHua]

Problem

we found out the datapointss of implicit workspace #6098 experiment is too low and majority of users do not turn on workspace context configurable

Solution

similar to #5856 which targets amz internal users, the team decided to try turn on (only once) the configurable for a small fraction of all users (20%)

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[github-actions]

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[Will-ShaoHua]

not quite sure if it's a "feat" or "config", personally i think "config" is better as it's a feature under testing and not officially launch

[Will-ShaoHua]

this PR will be included in 12/17 release