Enable `"test-support"` feature on editor dependencies for tests (#2499)

Enable the `"test-support"` feature whenever we depend on the `editor`
crate in tests.

If we don't do this, we end up depending on `livekit_client` without
enabling `"test-support"`, and this causes us to link against
`WebRTC.framework` in its build script, which causes a dynamic linker
error when starting the tests.

Fixes
https://linear.app/zed-industries/issue/Z-1646/cant-run-package-tests-for-activity-monitor-and-auto-update

Release Notes:

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