Move table names from constants to reader struct

[srikanthccv]

There are some table names defined as constants in reader.go and used for querying. https://github.com/SigNoz/signoz/blob/e39d2f799d14b495596dade12cf40b15e453b08f/pkg/query-service/app/clickhouseReader/reader.go#L52-L59

They should be moved to reader struct like many traces tables which exist already.

https://github.com/SigNoz/signoz/blob/0620cacb0b244752c8463dd0bb97453cac65a3f7/pkg/query-service/app/clickhouseReader/options.go#L103-L117