Helm Chart: make temporal and temporal_visibility databases configurable

## Tell us about the problem you're trying to solve
I'm willing to use the same postgresql instance/RDS for multiple Airbyte deployments.
To achieve this I have to preconfigure the databases such as airbte_db_1 airbte_db_2.
But - its not the only dependency, Airbyte deployment requires `temporal_visibility` and `temporal` databases as well ,but I can't preconfigure these when using helm chart deployment.

## Describe the solution you’d like
I'd like to have configuration sections for these databases just like the configuration for externaldatabase:
```
externalTemporalDatabase:
host: localhost
user:
password: ""
existingSecret: ""
existingSecretPasswordKey: ""
database: airbyte_temporal_1
port:

externalTemporalVisibilityDatabase:
host: localhost
user:
password: ""
existingSecret: ""
existingSecretPasswordKey: ""
database: airbyte_temporal_vis_1
port:
```