Restore azurerm_nginx_configuration resource and data source

[valyria257]

Reverts #24276

There are a couple of things here:

• The default configuration/import error issue was resolved. See changelog from March 13, 2024
• This is a breaking change from a product use-case perspective as it breaks our HTTPS use-case where in the workflow is:
  1. Create deployment.
  2. Create certificate.
  3. Create configuration.

With configuration now being inline, the use workflow breaks as 1 and 3 cannot be separated.

• certificates should also not be inline since different roles may mange deployments, certificates, and configurations separately

To fix this, the change to remove the azurerm_nginx_configuration is reverted, and the field that was added to replace it is deprecated.

[stephybun]

Duplicate of #25402

[valyria257]

@stephybun this PR supersedes #25402. Can you please reopen? cc: @puneetsarna

[puneetsarna]

@stephybun I am going to close mine. @valyria257 has changes that we need to deprecate the newer embedded fields and a test to establish the contract as well in addition to the restoration of the resource.

[valyria257]

Created a new PR instead: #25773

[github-actions]

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