feat(kuma-cp) proxy template V3 (bp #1398)

[mergify]

This is an automated backport of pull request #1398 done by Mergify

Cherry-pick of 5eaee19 has failed:

On branch mergify/bp/release-1.0/pr-1398
Your branch is up to date with 'origin/release-1.0'.

You are currently cherry-picking commit 5eaee1904.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   pkg/core/xds/resource.go
	modified:   pkg/xds/envoy/clusters/v3/circuit_breaker_configurer_test.go
	modified:   pkg/xds/envoy/clusters/v3/client_side_mtls_configurer_test.go
	modified:   pkg/xds/envoy/clusters/v3/client_side_tls_configurer_test.go
	modified:   pkg/xds/envoy/clusters/v3/eds_cluster_configurer.go
	modified:   pkg/xds/envoy/clusters/v3/eds_cluster_configurer_test.go
	modified:   pkg/xds/envoy/clusters/v3/lb_subset_configurer_test.go
	modified:   pkg/xds/generator/modifications/modifications.go
	renamed:    pkg/xds/generator/modifications/cluster.go -> pkg/xds/generator/modifications/v2/cluster.go
	renamed:    pkg/xds/generator/modifications/cluster_test.go -> pkg/xds/generator/modifications/v2/cluster_test.go
	renamed:    pkg/xds/generator/modifications/http_filter.go -> pkg/xds/generator/modifications/v2/http_filter.go
	renamed:    pkg/xds/generator/modifications/http_filter_test.go -> pkg/xds/generator/modifications/v2/http_filter_test.go
	renamed:    pkg/xds/generator/modifications/listener.go -> pkg/xds/generator/modifications/v2/listener.go
	renamed:    pkg/xds/generator/modifications/listener_test.go -> pkg/xds/generator/modifications/v2/listener_test.go
	new file:   pkg/xds/generator/modifications/v2/modifications.go
	renamed:    pkg/xds/generator/modifications/modifications_suite_test.go -> pkg/xds/generator/modifications/v2/modifications_suite_test.go
	renamed:    pkg/xds/generator/modifications/network_filter.go -> pkg/xds/generator/modifications/v2/network_filter.go
	renamed:    pkg/xds/generator/modifications/network_filter_test.go -> pkg/xds/generator/modifications/v2/network_filter_test.go
	renamed:    pkg/xds/generator/modifications/virtual_host.go -> pkg/xds/generator/modifications/v2/virtual_host.go
	renamed:    pkg/xds/generator/modifications/virtual_host_test.go -> pkg/xds/generator/modifications/v2/virtual_host_test.go
	new file:   pkg/xds/generator/modifications/v3/cluster.go
	new file:   pkg/xds/generator/modifications/v3/cluster_test.go
	new file:   pkg/xds/generator/modifications/v3/http_filter.go
	new file:   pkg/xds/generator/modifications/v3/http_filter_test.go
	new file:   pkg/xds/generator/modifications/v3/listener.go
	new file:   pkg/xds/generator/modifications/v3/listener_test.go
	new file:   pkg/xds/generator/modifications/v3/modifications.go
	new file:   pkg/xds/generator/modifications/v3/modifications_suite_test.go
	new file:   pkg/xds/generator/modifications/v3/network_filter.go
	new file:   pkg/xds/generator/modifications/v3/network_filter_test.go
	new file:   pkg/xds/generator/modifications/v3/virtual_host.go
	new file:   pkg/xds/generator/modifications/v3/virtual_host_test.go
	modified:   pkg/xds/generator/proxy_template.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   pkg/xds/envoy/clusters/v3/health_check_configurer_test.go

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