Dashboard: conditional logic in queries to handle Tempo / Jaeger / OpenSearch specific syntax to filter on undefined labels or on `All : .*` label values

<!-- Please only use this template for submitting feature requests --> **Why is this needed**: Key OpenTelemetry attributes for dashboard filtering, such as `deployment.environment.name` (e.g., `prod`, `staging`) and `service.namespace` (e.g., `webshop`, `team-ecommerce`), are often optional for ease of getting started. Consequently, they are frequently omitted initially and implemented later as systems scale. Tempo's TraceQL, OpenSearch PPL, or Jaeger don't support the same syntax as PromQL or LogQL for undefined labels, requiring different handling of variables in the Tempo TraceQL/ OpenSearch PPL / Jaeger query: | Database / Query Language | Label equality | Regular expression / pattern matching | Label NOT defined | Any Label value, including not defined | |--------------------------------------------|---------------------------------|-----------------------------------------------|-------------------------------------------------------------------------------------|-----------------------------------------------------| | Prometheus / PromQL | `{my_attr = "my_val"}` | `{my_attr =~ "my_pattern"}` | `{my_attr = ""}` or `{my_attr =~ ""}` | `{my_attr =~ ".*"}` | | Loki / LogQL | `{my_attr = "my_val"}` | `{my_attr =~ "my_pattern"}` | `{my_attr = ""}` or `{my_attr =~ ""}` | `{my_attr =~ ".*"}` | | Tempo / TraceQL | `{.my_attr = "my_val"}` | `{my_attr =~ "my_pattern"}` | [PR #4905](https://github.com/grafana/tempo/pull/4905) to support `{my_attr = nil}` | `{.my_attr =~ ".*"}` | | OpenSearch / PPL | `attributes.my_attr = "my_val"` | `my_attr = /my_pattern/ ` | `attributes.my_attr is null` | `my_attr = /.*/ ` | | Jaeger ElasticSearch with `tags-as-field` | | support wildcard `*` and probably regexes| | …