feat: add dump function for current connections count

[fengmk2]

No description provided.

[sidorares]

I'm probably +1 to expose this information somehow
At the same time I'd prefer to minimise surface api, since queryingConnectionsCount can be computed from other 3 maybe not worth adding

Also re naming: instead dumpConnectionsCount - maybe something like connectionsInformation or getConnectionsInformation. Also maybe idleConnectionsCount instead of freeConnectionsCount - need to check if related information is exposed under similar name

[sidorares]

looks like CI config need some refresh, potentially dropping node 0.10 and moving appveyor to actions windows runner

[fengmk2]

cc @qile222

[dougwilson]

Well, we don't want to remove node.js versions from the CI that are supported by the current version. Usually removing support is a semver major action. Taking a look, the CI appveypr seem to be fine, just the new code in the PR needs to be adjusted to actually work in Node.js 0.10 is all (I suspect it is the use of deepStrictEqual in the tests as I don't think thay existed then). And I will update gh actions runner host for those.

As for the change, it seems fine, though whay about just calling it getConnnectionCounts() or such?

[dougwilson]

Also, I think maybe queryingConnectionsCount is going to.be confusing, since the math for thay number is not the number of connections making a query, but just like the connection that are checked out from the pool, even if they are just idle.