feat(cpa): create project from example using `--example` CLI arg (#10172)

Adds the ability to create a project using an existing in the Payload
repo example through `create-payload-app`:

For example:
`pnpx create-payload-app --example custom-server` - creates a project
from the
[custom-server](https://github.com/payloadcms/payload/tree/main/examples/custom-server)
example.

This is much easier and faster then downloading the whole repo and
copying the example to another folder.
Note that we don't configure the payload config with the storage / DB
adapter there because examples can be very specific.