feat: jsdocs for generated types, by using admin.description

[AlessioGr]

This makes use of admin.description to generate JSDocs for field, collection and global generated types.

For the future, we should add a dedicated property to override these JSDocs.

You can view the effect of this PR on our test suite generated types here: https://github.com/payloadcms/payload/pull/9917/commits/05f552bbbc9f963f5b3145528eb089f05e7c86cb