[-] fix pgbouncer dashboard (#1002)

* change dashboard 1-global-db-overview

    Harmonise the layout of legends: in a list and at the bottom for all signs

* Fix the database name lookup in the pgbouncer dashboard

    since the metrics database model has changed, the actual database name is inside the JSON field data
    also clean some old and unused sql queries

* Add the variable monitoredsource to distinct dbname from sources

    the monitoredsource variable corresponds to the pgbouncer
    entries in the configuration.

* Pgbouncer Dashboard : hix monitoredsource query

* Make `$dbname` a multi-value variable

* Fix `Outgoing traffic rate' panel

* Disallow repeating in `time series` panel.

- all lines appear within the same panel.
- add `all` field to the `DB Name` multi-value.

* Rename grafana variable `$dbname` to `$databases`

- to avoid confustion the queries already have `dbname` column

* Make colors dynamic.

* Update the repeat variable name to `databases` from `dbname`.

* remove unnecessary object

* graph panel : fix window definition with database from json

* Pgbouncer database selector : add time filter

    prevent scanning all partitions

* Update grafana/postgres/v12/pgbouncer-stats.json

update dynamically on time range change

Co-authored-by: Ahmed Gouda <gouda0x@gmail.com>

* Update Database selector label

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Co-authored-by: Sébastien Lardière <s.lardiere@loxodata.com>
Co-authored-by: 0xgouda <gouda0x@gmail.com>

Author: 3 people