*: rewrite `interface{}` to `any`

The Go stdlib proposed this in https://github.com/golang/go/issues/49884 and made the change in https://github.com/golang/go/commit/2580d0e08d5e9f979b943758d3c49877fb2324cb.

This should be as straightforward as:
```
gofmt -w -r 'interface{} -> any' pkg
```

We probably don't want to do this right around a release, when we're performing many backports. Let's wait a month or so.

We should then also add a lint to detect any new uses of `interface{}`.

Jira issue: CRDB-33511