Migrate CustomConnectionSpec to include groupId

[shouples]

Interface update to include new property:

vscode/src/storage/resourceManager.ts

Lines 45 to 50 in a35be57

	export interface CustomConnectionSpec extends ConnectionSpec {
	// enforce `ConnectionId` type over `string`
	id: ConnectionId;
	/** The option chosen by the user to describe this connection. Similar to {@link ConnectionType} */
	formConnectionType: FormConnectionType;
	}

All currently stored specs should set groupId: null until the connection form allows setting it via new migration. https://github.com/confluentinc/vscode/tree/main/src/storage/migrations