fall back to internet for private DNS

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### Description

#### Is your feature request related to a problem?

When the module deploys private DNS zones for a service which does not have private link enabled, this can cause clients to fail to resolve DNS names for the zone. An example of this is Azure Monitor.

#### Describe the solution you'd like

I believe now we can configure on the private DNS zone->VNET link that the zone should fall back to internet resolution whenever the private DNS zone can't provide an answer.
I'm wondering if it might be a good idea to have the module configure this setting to be enabled by default and allow end users to set it as well.

Maybe there's something I'm missing, if anyone knows of a reason this should not be done please chime in.

#### Additional context

No files, tests, or entry points are named in the issue. Start by locating the module that creates private DNS zone-to-VNET links and verify how Azure's fallback-to-internet setting can be exposed, enabled by default, and overridden by users; done means affected names resolve through the internet when the private zone has no answer.

Written by the indexing model from the issue text.