SOLR-17458: Give request handler base errors its own metric

[mlbiscoc]

https://issues.apache.org/jira/browse/SOLR-17458

I feel that the cardinality of solr_metrics_core_requests_total was already high enough with the number of handlers + cores as labels and we are bloating it with 3 different types of errors client/server/timeouts. This makes things confusing and I think its justified errors has its own metric name called solr_metrics_core_requests_errors_total.

Makes it very easy as well to create its own error aggregation by just querying solr_metrics_core_requests_errors_total{} and you get all errors without needs to specify the type=errors label.

solr_metrics_core_requests_errors_total{category="QUERY",collection="demo",core="demo_shard1_replica_n1",handler="/select",internal="false",otel_scope_name="org.apache.solr",replica="replica_n1",shard="shard1",source="client"} 0.0
solr_metrics_core_requests_errors_total{category="QUERY",collection="demo",core="demo_shard1_replica_n1",handler="/select",internal="false",otel_scope_name="org.apache.solr",replica="replica_n1",shard="shard1",source="server"} 0.0
solr_metrics_core_requests_errors_total{category="QUERY",collection="demo",core="demo_shard1_replica_n1",handler="/select",internal="true",otel_scope_name="org.apache.solr",replica="replica_n1",shard="shard1",source="client"} 0.0
solr_metrics_core_requests_errors_total{category="QUERY",collection="demo",core="demo_shard1_replica_n1",handler="/select",internal="true",otel_scope_name="org.apache.solr",replica="replica_n1",shard="shard1",source="server"} 0.0
solr_metrics_core_requests_errors_total{category="QUERY",collection="demo",core="demo_shard1_replica_n1",handler="/select",internal="false",otel_scope_name="org.apache.solr",replica="replica_n1",shard="shard1",type="timeouts"} 0.0
solr_metrics_core_requests_errors_total{category="QUERY",collection="demo",core="demo_shard1_replica_n1",handler="/select",internal="true",otel_scope_name="org.apache.solr",replica="replica_n1",shard="shard1",type="timeouts"} 0.0

[dsmiley]

Please create PRs with a leading JIRA URL link. The PR template includes this. Personally, this is the only part I retain; I delete the rest.

[dsmiley]

+1