Allow globals to be accessed using API key

[Swahjak]

Problem
API key access can be configured on collections (https://payloadcms.com/docs/authentication/config#authenticating-via-api-key) but not
on globals, making it harder to access globals programmatically.

Solution
Allow useAPIKey (and possibly other auth options) to be set on globals

[Swahjak]

Seems like I mis interpreted the documentation. To me the sentence "To enable Authentication on a collection, define an auth property and set it to either true or to an object containing the options below." is unclear since it suggest that I can enable authentication on a per collection basis. This may seem obvious if you are familiar with payloads workflow, but most applications will probably work with a single user entity (or maybe two).