The `HighCPUUsage` alert is based on the `cpu_usage_percentage` metric.
Instead of exposing the overall CPU usage in percent, the metric exposes
the per core usage summed over all cores.
This commit removes the alert for two reasons:
1. Substrate itself does not expose the core count and thus one can not
alert based on the `cpu_usage_percentage` metric.
2. Alerting based on CPU usage is generic and not specific to Substrate
or Blockchains. Thus any CPU usage alert suffice.
The transaction queue size alert has been firing with a constant 10
transactions in the queue. While maybe problematic those 10 transactions
don't need to be the same across scrape intervals.
Instead of alerting with a size above 10, alert based on two things:
1. Monotonically increasing queue size
2. Upper limit queue size reached