Add ServiceGatewayClient to Azure client factory

[georgeedward2000]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Introduces a new ServiceGatewayClient in pkg/azclient/ for managing Azure Service Gateway resources via armnetwork/v9.

• Introduced ServiceGatewayClient interface and implementation for managing Azure Service Gateways
• Updated ClientFactory interface to include GetServiceGatewayClient() method
• Implemented standard CRUD methods (Get, CreateOrUpdate, Delete, List) via code generation
• Implemented custom methods: UpdateTags, GetAddressLocations, GetServices, UpdateAddressLocations, UpdateServices
• Added generated tests and mocks for ServiceGatewayClient
• Integrated metrics and tracing for all ServiceGateway operations
• Added rate limiting support via serviceGatewayRateLimit config key

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

The custom methods follow established patterns in the codebase:

• UpdateTags — non-LRO, follows virtualnetworkclient/custom.go pattern
• GetAddressLocations / GetServices — pager-based, follows interfaceclient/custom.go pattern
• UpdateAddressLocations / UpdateServices — LRO-based, follows privatelinkserviceclient/custom.go pattern

The generated integration tests (servicegatewayclient_test.go) require Azure credentials and a recorded cassette to pass locally — this is expected for all newly generated clients.

Does this PR introduce a user-facing change?

Added ServiceGatewayClient to the Azure client factory for managing Azure Service Gateway resources.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: georgeedward2000
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[k8s-ci-robot]

Hi @georgeedward2000. Thanks for your PR.

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[nilo19]

/ok-to-test

[nilo19]

/ok-to-test