admin: new API for creating KMS master keys (#9982)

This commit adds a new admin API for creating master keys.
An admin client can send a POST request to:
```
/minio/admin/v3/kms/key/create?key-id=<keyID>
```

The name / ID of the new key is specified as request
query parameter `key-id=<ID>`.

Creating new master keys requires KES - it does not work with
the native Vault KMS (deprecated) nor with a static master key
(deprecated).

Further, this commit removes the `UpdateKey` method from the `KMS`
interface. This method is not needed and not used anymore.

cmd/admin-router.go

@@ -197,6 +197,7 @@ func registerAdminRouter(router *mux.Router, enableConfigOps, enableIAMOps bool)
 
 		// -- KMS APIs --
 		//
+		adminRouter.Methods(http.MethodPost).Path(adminVersion+"/kms/key/create").HandlerFunc(httpTraceAll(adminAPI.KMSCreateKeyHandler)).Queries("key-id", "{key-id:.*}")
 		adminRouter.Methods(http.MethodGet).Path(adminVersion + "/kms/key/status").HandlerFunc(httpTraceAll(adminAPI.KMSKeyStatusHandler))
 
 		if !globalIsGateway {