Test/Enable Node.js 14 support for noSQL connectors

[dhmlau]

Originated from epic: #6019

Acceptance Criteria

For the following connectors, test locally on Node.js 14 and see if all tests passed.

• If yes, add Node.js 14 to CI
• If not, try to fix it for simple fixes. If you don't think you can fix it in a day, open a new issue to keep track of it.

Here is the list of connectors:

• loopback-connector-mongodb
• loopback-connector-couchdb2
• loopback-connector-cloudant
• loopback-connector-cassandra

[dhmlau]

We've included Node.js 14 in jenkins, so tests on Node.js14 should be ran automatically without any changes.

Verified loopback-connector-couchdb2 works with Node.js 14. See loopbackio/loopback-connector-couchdb2#82

[dhmlau]

Closing as done.
Node.js 14 is enabled in Jenkins for all repos.