Remove usage of deprecated mongo methods

[ejizba]

Related to #1281 (comment) and #1298, seems like we're using deprecated mongo methods in a few places. We should go through and fix all of those

A few examples: count, remove, insert

[ejizba]

Also we're seeing this in the Mongo output window on activation:

the options [appName] is not supported
[Error - 11:15:02 AM] (node:81124) DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to the MongoClient constructor.

[nturinski]

I think the options appName portion is related to a change I made for private endpoints.

#1262

[ejizba]

I looked into preventing the output channel from popping up, but it's a little complicated because it's not our default output channel, it's an output channel handled by the "vscode-languageclient" module. There's an option "revealOutputChannelOn", but if I set it to "Never" that hides all errors and I'm not sure I'm ready to commit to that on short notice. Will move to the next milestone

Also - doesn't affect all users of the extension, just ones that have connected a Mongo db.