Add possibility to manually set privatelink partition ids for azure static apps

[gittyNico]

Overview/Summary

Azure static web apps are currently spawned without a known pattern in Public DNS zones with different partition ids in their FQDN. We are now counting [1,2,3,4,5].azurestaticapps.net with a unknown rising number.
Private DNS Zones are used for private Endpoints correspondingly (privatelink.[1,2,3,4,5].azurestaticapps.net.) and as of the CAF principals need to be known before deploying the first resources.

There is no programmatic approach known to me.

Feel free to adjust to your needs.

Examples for module calls:

# Adds all at PR time available: default + 1-5
configure_connectivity_resources = {
    ...
    advanced = {}
}

# Adds only zones: default + 4 + 5
configure_connectivity_resources = {
    ...
    advanced = {
      custom_privatelink_azurestaticapps_partitionids = [4, 5]
    }
}

This PR fixes/adds/changes/removes

1. Adds all currently existing private DNS zones per default, when 'azure_web_apps_static_sites' is set to true.
2. Adds possibility to manually define a list of partition ids wanted. (Prohibits a breaking change when Microsoft adds a new partitionid)

Breaking Changes

none

Testing Evidence

• I did a plan on our current infrastructure and had no changes (all five private DNS Zone currently deployed)
• Also tested the default behavior when not setting the new variable

As part of this Pull Request I have

• Checked for duplicate Pull Requests
• Associated it with relevant issues, for tracking and closure.
• Ensured my code/branch is up-to-date with the latest changes in the main branch
• Performed testing and provided evidence.
• Updated relevant and associated documentation.

[gittyNico]

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