fix: schema option on run-ios not installing and loading the right bundle

[misoguy]

Summary:

This PR adds schema folder to the ios build path
to resolve issue facebook/react-native#20497

Test Plan:

1. Setup a different scheme with different environment variables for the same app. ex) exampleApp, exampleAppDev
2. run react-native run-ios --scheme exampleApp
3. should install and run exampleApp with a variable
4. run react-native run-ios --scheme exampleAppDev
5. should install and run exampleAppDev with b variable

[misoguy]

@thymikee I could have a default value for the scheme but I think the scheme is always present with a default as this line is using it as a backup for appName. Let me know your thoughts :)

[thymikee]

Oh, it wasn't clear by looking at the diff. Then it looks like it's all good, anybody would like to test that? :)

[grabbou]

Looks good. Tested locally. Shipping. Thank you <3