[Capella] Add Dev/Stage certificates to `gocbcore`

What's the issue?
As it stands, we bundle the Capella certificate in gocbcore, allowing customers to connect to their databases without requiring them to setup the SDK with that certificate.

We only bundle the Prod certificate though, and not the ones from our Dev/Stage environments; while this won't affect customers, it makes development slightly more challenging.

For example: We have to supply certs to the SDK for Dev/Stage, but not in Prod making our code branch'ier than it need be.

What's the fix?
Please could we bundle the Dev/Stage certificates as well.

We do this in cbbackupmgr (source).