`server` label is not added consistently to metrics

[KulykDmytro]

Hi

At 0.15 running for of RDS instance (in kubernetes) we observing following behaviour. on default settings + queries.yaml These collectors provides server label, other not:

• all metrics passed over queries.yaml
• pg_settings
• pg_stat_activity
• pg_stat_archiver
• pg_stat_database (only for conflicts_confl section)
• pg_static

expected that labeling will be consistent (all on or all off) or at least configurable per collector

Environment

AWS EKS

• System information:

Linux 5.10.214-202.855.amzn2.x86_64 x86_64

• postgres_exporter version:

postgres_exporter, version 0.15.0 (branch: HEAD, revision: 68c176b8833b7580bf847cecf60f8e0ad5923f9a)
  build user:       root@88f74f2c2888
  build date:       20231027-14:38:56
  go version:       go1.21.3
  platform:         linux/amd64
  tags:             unknown

• postgres_exporter flags/variables:

variables:
  PG_EXPORTER_EXCLUDE_DATABASES: rdsadmin
  PG_EXPORTER_EXTEND_QUERY_PATH: '/var/lib/postgresql/queries.yaml'

• PostgreSQL version: 14.10.0 (AWS RDS)