Substrate alerts rules update (#10642)

* .maintain/monitoring: Update substrate prometheus alert rules

* match the `substrate_` metrics prefix in alerts instead of `polkadot_`, following changes in #9543
* remove the filtering on polkadot|kusama domain for NumberOfFileDescriptorsHigh alert

* .maintain/monitoring: Update substrate Grafana dashboards

* match the `substrate_` metrics prefix instead of `polkadot_` in dashboards, following changes in #9543

* .maintain/monitoring:  make the NumberOfFileDescriptorsHigh alert only apply for metrics tagged with 'chain'