[E2E Tests] Cover Instance vs. Subaccount vs. Provider vs. Subscriber Destinations in Non-DwC Test

[MatKuhr]

Currently, our E2E tests do not cover the difference between /instanceDestinations and /subaccountDestinations. (at least I couldn't find any place).

Ensure our E2E tests cover all 6 following cases:

• provider + instance
• provider + subaccount
• subscriber + override via ALWAYS_PROVIDER+ instance
• subscriber + override via ALWAYS_PROVIDER+ subaccount
• subscriber + instance
• subscriber + subaccount

We should have the same destination name for all 6 cases, but different properties, such that we can assert for each case if the correct destination was fetched