ospp: Feature/traffic

[maxingg]

What this PR does:
Optimize the traffic filter, and make cluster config support both header and weight strategy.

Which issue(s) this PR fixes:

Fixes #402

[codecov-commenter]

Codecov Report

Merging #496 (2ece16e) into develop (5301405) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #496      +/-   ##
===========================================
- Coverage    54.97%   54.90%   -0.08%     
===========================================
  Files          662      662              
  Lines        77433    77433              
===========================================
- Hits         42572    42512      -60     
- Misses       31246    31296      +50     
- Partials      3615     3625      +10     

Impacted Files	Coverage Δ
security/pkg/credentialfetcher/fetcher.go	40.00% <0.00%> (-20.00%)	⬇️
pkg/kube/inject/watcher.go	48.14% <0.00%> (-8.65%)	⬇️
pkg/kube/controllers/queue.go	55.22% <0.00%> (-7.47%)	⬇️
pkg/istio-agent/xds_proxy_delta.go	48.18% <0.00%> (-7.26%)	⬇️
pkg/test/util/retry/retry.go	57.14% <0.00%> (-3.58%)	⬇️
pkg/istio-agent/xds_proxy.go	59.43% <0.00%> (-3.26%)	⬇️
pilot/pkg/xds/monitoring.go	78.57% <0.00%> (-2.86%)	⬇️
istioctl/cmd/wait.go	72.47% <0.00%> (-2.25%)	⬇️
pilot/pkg/bootstrap/server.go	53.11% <0.00%> (-1.07%)	⬇️
...g/serviceregistry/kube/controller/endpointslice.go	73.44% <0.00%> (-0.69%)	⬇️
... and 3 more

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