start() and stop() methods in MapeoManager should be renamed or removed

[achou11]

Description

the initial thinking was that they'd be generalized for starting/stopping a few internal things, but turns out that it's really only managing the media server.

Tasks

One of the following:

• Rename start() to startMediaServer() and stop() to stopMediaServer()(see rename MapeoManager.start() and MapeoManager.stop() methods #399)
• Expose the media server, which has those methods i.e. get mediaServer() { return this.#mediaServer }