docker: standardize file permissions of files in container (#38068)
docker: standardize file permissions of files in container (#38068)

All files will be 644 or 755, depending on if they are executable or
not.

Fixes https://github.com/istio/istio/issues/37151.

This was made worse in https://github.com/istio/istio/pull/37935, which
accidentally removed `chmod` on the echo certs; this makes anyone not
running as root not able to build functional images
istio/istio,istio/istio,istio/istio,istio/istio,istio/istio