Migrate edit_prediction_provider setting before updating its value to 'zed' during onboarding #43210

Job	Run time
Check Postgres and Protobuf migrations, mergability	12s
(macOS) Run Clippy and tests	6m 48s
(Linux) Run Clippy and tests	12m 17s
(Linux) Build Remote Server	2m 3s
Check formatting and spelling	26s
(Windows) Run Clippy and tests	15m 54s
Create a macOS bundle	0s
Linux arm64 release bundle	0s
Linux x86_x64 release bundle	0s
Auto release preview	0s
	37m 40s

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