logging - rename hostname to domain

Summary

In the bigbang values.yaml the first yaml key-pair is
hostname: bigbang.dev
This key is incorrectly named. This is a DOMAIN not a hostname. The key name should be
domain:
This incorrect name cascades down into all the Package repos.

Solution

1. Modify Package chart. Change chart/values.yaml

   hostname: bigbang.dev
   to
   domain: bigbang.dev

   search for all helm template occurrences of .Values.hostname and replace with .Values.domain. Expect them in the istio section of the chart/values.yaml. But there could be other locations where the key is used.
2. When the BigBang MR is created you should modify the values template
   chart/templates/<package>/values.yaml
   to remove the hostname key because the Package will no longer need this value passed down.

   # hostname is deprecated and replaced with domain. But if hostname exists then use it.
   {{- $domainName := default .Values.domain .Values.hostname }}
   hostname: {{ $domainName }}
   domain: {{ $domainName }}

3. Test a BigBang Package deployment with
   hostname: bigbang.dev
   and with
   domain: bigbang.dev
   to insure that both still work.