Private DNS Zone update for new regions

[Springstone]

This pull request updates the Private DNS Zones policy assignment parameters to include support for new Azure regions and ensures region codes are consistent and comprehensive across templates. The changes add several newly launched Azure regions, restore a few previously removed regions, and update the documentation to reflect these improvements.

Private DNS Zones region support updates:

• Added new Azure regions and their geo short codes (e.g., austriaeast, belgiumcentral, chilecentral, denmarkeast, malaysiawest, taiwannorth, taiwannorthwest) to both eslzArm.json and DINE-PrivateDNSZonesPolicyAssignment.json for Private DNS Zones policy assignments. [1] [2] [3] [4]
• Restored previously omitted regions (centraluseuap, eastus2euap, jioindiacentral, jioindiawest) to ensure full coverage and backward compatibility. [1] [2]

Documentation update:

• Updated the "What's New" documentation to note the expanded region support for Private DNS Zones in the portal accelerator.

[jtracey93]

Please also update the portal deployment e.g.:

• https://github.com/Azure/Enterprise-Scale/blob/main/eslzArm/eslzArm.json#L2223-L2298

[Springstone]

Please also update the portal deployment e.g.:

• https://github.com/Azure/Enterprise-Scale/blob/main/eslzArm/eslzArm.json#L2223-L2298

Please also update the portal deployment e.g.:

• https://github.com/Azure/Enterprise-Scale/blob/main/eslzArm/eslzArm.json#L2223-L2298

@jtracey93 Yea, need to revise this list of regions, which is also incorrect. But will update the deployment as well.