Refactor the proxy injection logic in the pkg/inject/inject.go file to work with the new Helm chart. The main changes will be instead of relying on the k8s.io/api/* packages to build the proxy and proxy-init spec in Go, the spec will be read from the new partials and rendered by the Helm's library to produce the full injected YAML.

This task includes creating the patch chart.

Tests should cover the auto injection, and linkerd inject and linkerd inject --manual scenarios.

Depends on #3126.