[DO NOT MERGE] Test azure-c-shared-utility socket retry fix in Event Hubs

[Johnathan W (j7nw4r)]

Purpose

Validates Azure/azure-c-shared-utility#683 in the Event Hubs SDK before the next azure-c-shared-utility release.

Changes

• Adds a repository-owned vcpkg overlay for azure-c-shared-utility.
• Backports PR Azure::Core #683 and its prerequisite, PR #684, onto the source revision used by the current vcpkg port.
• Selects the overlay automatically during Azure SDK CMake configuration.

A direct pin to the PR merge commit is not used because that revision references additional unreleased dependency and submodule revisions that are incompatible with the current Azure SDK vcpkg baseline.

Testing

• Configured successfully with vcpkg and the vendored uAMQP implementation.
• Built azure-c-shared-utility in Debug and Release configurations.
• Built the azure-messaging-eventhubs-test target.
• Ran 119 selected Event Hubs tests in playback mode with no failures. Live-only tests were skipped, and the credential-dependent checkpoint test was excluded.

Notes

DO NOT MERGE. This PR exists only to enable validation builds. The overlay should be removed in favor of the released dependency update.

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