Make uint64 support permanently enabled

[e-dard]

In 2.0 we should have full uint64 support enabled. This issue is to track cleaning up the technical debt left from when we had uint64 behind a build flag.

Start by removing this:

influxdb/models/points.go

Line 70 in d33ea6e

var enableUint64Support = false

And go from there...

By the end, there should be no option to enable/disable uint64 support throughout the codebase.

[nwneisen]

I'm interested in working on this but it looks like @ayang64 has already made the change. Is this PR just needing a signed CLA and verification that tests are passing?

[e-dard]

@nwneisen yep, Ayan took that one. It's great to see interest in contributing from the community. There is another issue here labelled as a good starter here: #15571

What sorts of things are you interested in within the code-base?

[nwneisen]

@e-dard I had started taking a look at #15571 after commenting.

At the moment, I'm interested in working in areas that would make me better at using InfluxDB. I answered some questions on stack overflow for Telegraf and there were some for InfluxDB that I thought I would try to answer also.

I was going to take a look at issues tagged with difficulty/low next. If there are any areas you view as higher priority, let me know and I will go for them first.