feature: Add suffix to schema type filenames

[calvincestari]

Fixes apollographql/apollo-ios#2598.

Users now have the codegen configuration option (appendSchemaTypeFilenameSuffix) to have a suffix added to their schema type filenames. This will help resolve problems in Xcode where the name of a schema type and operation type are the same causing a build error.

This new config option has a default value of false which means this should have no effect on users without the filename conflict error.

[netlify]

✅ Deploy Preview for eclectic-pie-88a2ba ready!

Name	Link
🔨 Latest commit	5743c59
🔍 Latest deploy log	https://app.netlify.com/sites/eclectic-pie-88a2ba/deploys/678af5754c105700080dd6b2
😎 Deploy Preview	https://deploy-preview-580--eclectic-pie-88a2ba.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[svc-apollo-docs]

✅ Docs preview ready

The preview is ready to be viewed. View the preview

File Changes

0 new, 1 changed, 0 removed

* (developer-tools)/ios/(latest)/code-generation/codegen-configuration.mdx

Build ID: 9d04abe4e703ef5acab42d0d

URL: https://www.apollographql.com/docs/deploy-preview/9d04abe4e703ef5acab42d0d

[netlify]

✅ Deploy Preview for apollo-ios-docc canceled.

Name	Link
🔨 Latest commit	5743c59
🔍 Latest deploy log	https://app.netlify.com/sites/apollo-ios-docc/deploys/678af575f9e6a0000869136d

[AnthonyMDev]

Just one issue to be resolved with the way the editable generated files are handled.

We also need to add this new option to the documentation (not just the generated docs).

[AnthonyMDev]

The old versions of these scalar files need to be deleted. But this actually surfaces a bigger issue here.

If a user had this new config false and then sets it to true, previously generated custom scalars (and any other files that are marked to not be overwritten) will not be handled properly. We need to preserve the changes to the code the user may have made. So we actually need to detect the old file name and rename the existing file, rather than just writing a new file.

[calvincestari]

OK, this is now done too. Logic in 6a22d37 and tests in 5743c59.

[AnthonyMDev]

I think we need tests that validates that when this is set to true that is reads it and writes it to the config properly.

[calvincestari]

Done in 34fea8b.

[calvincestari]

This PR already updated the codegen configuration documentation - Here it is in the docs preview for this PR. Is there another place in the docs to update?

I'll take a look at the other two review comments now..