Add config flow for Emby integration

[pantherale0]

Proposed change

I've added a fairly basic ConfigFlow here, there isn't much validation performed (the underlying library doesn't seem to expose much functionality to help with validating credentials etc. but it does seem like both could do with a bit of attention).

To do this, the dynamic entity creation and removal logic had to be removed (for now) as I fear it would introduce too many changes for a single PR. I'd like to overhaul the media_player platform too and create base entity / device classes but that will need to be done after this PR is complete and the device addition/removal logic is added back in (elsewhere).

As an aside, there is this custom integration out in the wild that currently doesn't work - https://community.home-assistant.io/t/new-emby-jellyfin-integration/576888

Type of change

• Dependency upgrade
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• This PR fixes or closes issue: fixes #
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[home-assistant]

Hey there @mezz64, mind taking a look at this pull request as it has been labeled with an integration (emby) you are listed as a code owner for? Thanks!

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