Combine channel /convert and /privacy endpoints

Description

Right now we have a /privacy API endpoint that allows to change the privacy (public, private) of a channel, and a /convert endpoint that allows to make a public channel private. We should decide how to combine these two endpoints in one as their functionality overlaps, and create a deprecation plan if needed.

QA Test Steps

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Status

Mana

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Assignee

Unassigned

QA Assignee

None

Reporter

Miguel de la Cruz

Epic Link

None

Fix versions

Mattermost Team

Platform

Sprint

Labels

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QA Testing Areas

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GitHub Issue

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Components

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