Fix issues with mismatched rlimit types on FreeBSD

[rhclayto]

On FreeBSD, the type for rlimit.max & rlimit.cur are int64. Currently cloudsql-proxy expects them to be uint64. This pull request casts the type of rlimit.cur & rlimit max to uint64, & casts the value of the passed inwantFDs to int64 when trying to assign it to rlim.Cur & rlim.Max.

See perkeep/perkeep#925 & https://camlistore-review.googlesource.com/c/camlistore/+/10147/ for other projects where this has reared its head.

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[rhclayto]

I have applied for the CLA. Waiting for it to take effect.

[googlebot]

CLAs look good, thanks!

[kurtisvg]

The license for a new file should be updated to 2019 Google LLC.

[mhoran]

I just ran into this yesterday and would love to see this merged. The proposed change resolves the issue on my machine.

[mhoran]

@kurtisvg is the copyright notice the only blocker for getting this merged? You may be able to fix that yourself if the author did not disable the option for reviewers to make changes to PRs. Otherwise I can resubmit this PR with the requested changes if @rhclayto isn't around to do it.

[broady]

LGTM. Copyright notice is not a blocker.