feat!: Add monitoring of Scaling Long Running Operations (#223)

* feat!: Store LRO ID in state object

BREAKING CHANGE: Spanner State Store requires DB schema update.

Store the Scaling Operation ID in the State object and
check it next time scaler runs.

This allows scaler to pull operation failure messages from the LRO, and
also to use the LRO completion time as the last successful scaling time
for cooldown.

Update readme and terraform with new Spanner schema defs

```sql
ALTER TABLE spannerAutoscaler ADD COLUMN IF NOT EXISTS lastScalingCompleteTimestamp TIMESTAMP;
ALTER TABLE spannerAutoscaler ADD COLUMN IF NOT EXISTS scalingOperationId STRING(MAX);
```

* fix: Update package-lock.json

fix: Update package-lock.json

* fix: await on async write to spanner

* fix: review comments.

README.md

@@ -155,6 +155,8 @@ used to monitor the behavior of the autoscaler, and to configure alerts.
  maximum configured size.
  * `WITHIN_COOLDOWN` - when the instance has been recently rescaled,
  and the autoscaler is waiting for the cooldown period to end.
+ * `IN_PROGRESS` - when an instance scaling operation is still
+ ongoing.
 
 ## Configuration