Cleanup webapp only actions/reducers/selectors from mattermost-redux

Description

There are a lot of actions that are only needed or used from the webapp (all the admin actions/selectors/reducers, for example) we can remove then from mattermost-redux and move them back to mattermost-webapp.

QA Test Steps

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Mana

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Assignee

Unassigned

QA Assignee

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Reporter

Jesús Espino

Epic Link

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Fix versions

Mattermost Team

Apps

Sprint

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Labels

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QA Testing Areas

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GitHub Issue

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