int32 need to be changed to uint32

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**Bug description**
As above, there are some fields in both http and tcp connection pool in DestinationRule which value default to 2^32-1，but the field type is int32。Maybe type of those fields should be changed to uint32 ?

The file is here:
https://github.com/istio/api/blob/master/networking/v1alpha3/destination_rule.pb.go

**Affected product area (please put an X in all that apply)**

[ ] Configuration Infrastructure
[ ] Docs
[ ] Installation
[X ] Networking
[ ] Performance and Scalability
[ ] Policies and Telemetry
[ ] Security
[ ] Test and Release
[ ] User Experience

**Expected behavior**
change the type of relative fields to uint32
**Steps to reproduce the bug**

**Version (include the output of `istioctl version --remote` and `kubectl version`)**

**How was Istio installed?**

**Environment where bug was observed (cloud vendor, OS, etc)**

Additionally, please consider attaching a [cluster state archive](http://istio.io/help/bugs/#generating-a-cluster-state-archive) by attaching
the dump file to this issue.