Clarify difference in virtual vs. physical DBRPs when listing

[candrewlee14]

Virtual DBRPs do not behave like physical DBRPs. Most importantly, they are read-only. If a user sees the virtual DBRPs in the current list format of influx v1 dbrp list, they might not realize that they are immutable. Separating the list table into two, physical DBRPs and virtual DBRPs, would make the behavior difference more clear to users.

[sanderson]

Add to the influx v1 dbrp list -h output:

Virtual DBRP mappings (InfluxDB OSS only) are created automatically using the bucket name. Virtual mappings are read-only. To modify a virtual DBRP mapping, create a new, explicit DBRP mapping. For more information, see https://docs.influxdata.com/influxdb/latest/query-data/influxql/dbrp/

[samhld]