remote projects per user (#10594)

Release Notes:

- Made remote projects per-user instead of per-channel. If you'd like to
be part of the remote development alpha, please email hi@zed.dev.

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Co-authored-by: Bennet Bo Fenner <53836821+bennetbo@users.noreply.github.com>
Co-authored-by: Bennet <bennetbo@gmx.de>
Co-authored-by: Nate Butler <1714999+iamnbutler@users.noreply.github.com>
Co-authored-by: Nate Butler <iamnbutler@gmail.com>