Open URIs from the CLI, support for the `zed://` URI scheme on Linux

[korewaChino]

Allows Zed to open custom zed:// links (redirects from https://zed.dev/channels) on Linux used XDG MIME types.

This PR also allows the CLI to be able to open Zed (zed://) URIs directly instead of executing the main executable in /usr/libexec/zed-editor.

Release Notes:

• Linux: Allow zed.dev/channel (zed://) URIs to open on Linux
• CLI: Ability to open URIs from the command line