Fix ExtensionsExtender to generate auditlog extension only if auditlog data exists

[koala7659]

Fix for a bug in Extension Extender for a situation when auditog configuration is not configured for given runtime region.

In such a case for created shoot we do not specify auditConfig.auditPolicy fields but we a attempting to add auditlog extension with empty data - so we have invalid and not expected extension for non existing auditLog configuration.

As a result generated shoot input is rejected and shoot creation fails with error:

{"level":"error","ts":"2024-12-10T14:43:27Z","msg":"Failed to create new gardener Shoot","runtimeID":"78b263d1-ecec-4373-abf4-d7993481261b","shootName":"c-4c21fef","requestID":28,"error":"admission webhook \"validator.shoot-auditlog-admission.extensions.gardener.cloud\" denied the request: [serviceURL: Required value: serviceURL must not be empty, tenantID: Required value: tenantID must not be empty]",",

Fix for Shoot creation and update when auditLogData for given Runtime region is empty.

• When creating a Shoot AuditLog extension is not added for new Shoot
• When updating a Shoot without AuditLog extension - empty AuditLog extension is not added to existing shoot extensions
• When updating a Shoot with existing AuditLog extension - the old extension remains in the list of existing shoot extensions