feat: support static credentials

[Jorres]

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Feature Request

Describe the Feature Request

At this point, operator is unable to connect to the database if enforce_static_user_credentials in Storage config is set to true

Relevant error:

2022-12-23T11:00:29.252Z	ERROR	controller.storage	GetSelfCheckResult error	{"reconciler group": "ydb.tech", "reconciler kind": "Storage", "name": "main", "namespace": "ydb", "error": "rpc error: code = Unauthenticated desc = unauthenticated,  Access denied without user token"}
github.com/ydb-platform/ydb-kubernetes-operator/internal/controllers/storage.(*Reconciler).Reconcile
	/workspace/internal/controllers/storage/controller.go:63

Additional Context

Internal ticket YDBOPS-6056