fix(NODE-6151): MongoClient connect does not keep Node.js running

[W-A-James]

Description

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Release Highlight

ref()-ed timer keeps event loop running until client.connect() resolves

When the MongoClient is first starting up (client.connect()) monitoring connections begin the process of discovering servers to make them selectable. The ref()-ed serverSelectionTimeoutMS timer keeps Node.js' event loop running as the monitoring connections are created. In the last release we inadvertently unref()-ed this initial timer which would allow Node.js to close before the monitors could create connections.

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