Update WPGraphQL to v1.22.1

[alecgeatches]

Description

Update WPGraphQL to the latest version (v1.22.1). This PR will also convert WPGraphQL to use a git subtree instead of the more manual copying previously used.

In the future, we can use this command to update WPGraphQL:

git subtree pull --prefix lib/wp-graphql git@github.com:wp-graphql/wp-graphql.git tags/<version> --squash

# e.g.
# git subtree pull --prefix lib/wp-graphql git@github.com:wp-graphql/wp-graphql.git tags/v1.22.1 --squash

Steps to Test

Outline the steps to test and verify the PR here.

Example:

1. Check out PR.
2. Run npm run build.
3. Test the thing.`
4. Verify cookies are delicious.

[alecgeatches]

Using git subtree has one main disadvantage, which is that WPGraphQL requires composer dependencies installed:

The vendor/ folder in WPGraphQL is .gitignored, which makes it difficult to make this a automated process.

I think for now, I'll revert to the old method of copying over new plugin files to avoid dependency issues.