fix: only add PSC ipType if PSC is enabled

[jackwotherspoon]

With CAS-based instances being supported soon and also using dnsName,
we can no longer rely on the presence of dnsName in the connectSettings
API as identifying that PSC is enabled on an instance.

Instead we should check pscEnabled from the response as source of truth.

Check if pscEnabled is True before setting PSC ip type.

Moving parseIPAddresses into private method on SQLAdminFetcher

[hessjcg]

Add new testcases for the new logic. Don't replace the existing testcases in test/sqladmin-fetcher-ts.

I'm curious about why you decided to inline the logic from parseIpAddresses() into the SqlAdminFetcher and get rid of the unit tests.

[hessjcg]

LGTM