Use a single db connection in functions repository methods

[bisgaard-itis]

Several of the methods in https://github.com/ITISFoundation/osparc-simcore/blob/ddc3e74b79c52718e17733c0720c5193b4be5fba/services/web/server/src/simcore_service_webserver/functions/_functions_repository.py open and close many db connections. There should only be a single open-close db connection for each of these methods.

• This was likely one of the issues in: https://monitoring.osparc-staging.io/graylog/messages/graylog_250/b4041241-46c6-11f0-ab1d-0242c0a80103
• Related: Upgrade FunctionJob retrieval endpoints for higher speed (Voyager) #1899

[bisgaard-itis]

@sanderegg this is the place in the code:

• https://github.com/ITISFoundation/osparc-simcore/blob/master/services/web/server/src/simcore_service_webserver/functions/_functions_repository.py#L225

It would make sense to handle all the functions within that file in a single PR

[sanderegg]

closed by ITISFoundation/osparc-simcore#7904