TimescaleDB metrics support

[Vonng]

we can collect timescaledb metrics for hypertables and chunks

#==============================================================#
# 1000 pg_tsdb_hypertable
#==============================================================#
# this collector reqires timescaledb extension to be installed
pg_tsdb_hypertable:
  name: pg_tsdb_hypertable
  desc: TimescaleDB hypertable overview
  query: |-
    SELECT current_database() AS datname,
           format('"%I"."%I"', hypertable_schema, hypertable_name) AS relname,
           num_dimensions AS dimensions, num_chunks AS chunks,
           compression_enabled::BOOLEAN::int AS compressed,
           hypertable_size(format('"%I"."%I"', hypertable_schema, hypertable_name)) AS bytes
    FROM timescaledb_information.hypertables;

  ttl: 10
  min_version: 100000
  tags: [ "extension:timescaledb", "schema:timescaledb_information" ]
  metrics:
    - datname:         { usage: LABEL ,description: database name }
    - relname:         { usage: LABEL ,description: Hypertable relation name }
    - dimensions:      { usage: GAUGE ,description: Number of partitioning dimensions }
    - chunks:          { usage: GAUGE ,description: Total chunks of this hypertable }
    - compressed:      { usage: GAUGE ,description: 1 if compression enabled }
    - bytes:           { usage: GAUGE ,description: Total size of hypertable in bytes }