Warn before ejecting that some config needs to be set on dynamic config

[brentvatne]

This PR adds some checks before proceeding with ejecting to ensure that it's compatible with app.config.[ts/js]

✖ We are unable to continue with ejecting until you make the following changes to app.config.ts:
- name: A project name is required.
- ios.bundleIdentifier: An iOS bundle identifier is required. Details.
- android.package: An Android package is required. Details.

[EvanBacon]

We have some e2e tests which currently attempt to lock the old app.json modification behavior down, be sure to update those to ensure these use-cases are air-tight

expo-cli/packages/expo-cli/src/commands/__tests__/upgrade-test.ts

Lines 292 to 323 in 8678009

	it(`delete the app.json sdkVersion if it's defined`, async () => {
	require('@expo/config').writeConfigJsonAsync = jest.fn((...props) => {
	return jest.requireActual('@expo/config').writeConfigJsonAsync(...props);
	});
	const projectRoot = '/from-app-json';
	await upgradeAsync(
	{ projectRoot, workflow: 'bare', requestedSdkVersion: null },
	{ yarn: true }
	);
	expect(require('@expo/config').writeConfigJsonAsync).toBeCalledTimes(1);
	expect(require('@expo/config').writeConfigJsonAsync).toHaveBeenLastCalledWith(projectRoot, {
	sdkVersion: undefined,
	});
	const { exp, rootConfig: json } = await require('@expo/config').readConfigJsonAsync(
	projectRoot
	);
	expect(json.expo.sdkVersion).not.toBeDefined();
	// Uses expo package version
	expect(exp.sdkVersion).toBe('35.0.0');
	}, 10000);
	// Important to ensure that we don't modify the app.json extraneously
	it(`skips modifying the app.json if the app.json doesn't define an sdkVersion`, async () => {
	require('@expo/config').writeConfigJsonAsync = jest.fn();
	const projectRoot = '/from-app-config-js';
	await upgradeAsync(
	{ projectRoot, workflow: 'bare', requestedSdkVersion: null },
	{ yarn: true }
	);
	expect(require('@expo/config').writeConfigJsonAsync).toBeCalledTimes(0);
	}, 10000);

[EvanBacon]

This might be the only warning that isn't covered now

[EvanBacon]

I've modified this so the entryPoint is simply deleted upon ejection. In a static config, this should be persisted, otherwise it won't matter because every eject will delete the field.