[kube-state-metrics] add additional environment variables support.

[liangyuanpeng]

What this PR does / why we need it

KSM support additional environment, in my case, i want to enable some client-go features with environment.

tested:

set env with normal

helm upgrade ksm .  --set "env[0].name=KUBE_FEATURE_ClientsAllowCBOR"  --set "env[1].name=KUBE_FEATURE_ClientsPreferCBOR" --set "env[0].value='true'" --set "env[1].value='true'" -i

and got the environment:

    Environment:
      KUBE_FEATURE_ClientsAllowCBOR:   'true'
      KUBE_FEATURE_ClientsPreferCBOR:  'true'

set env with autosharding.

helm upgrade ksm . --set "autosharding.enabled='true'" --set "env[0].name=KUBE_FEATURE_ClientsAllowCBOR"  --set "env[1].name=KUBE_FEATURE_ClientsPreferCBOR" --set "env[0].value='true'" --set "env[1].value='true'" -i

and got the environment:

    Environment:
      POD_NAME:                        ksm-kube-state-metrics-0 (v1:metadata.name)
      POD_NAMESPACE:                   default (v1:metadata.namespace)
      KUBE_FEATURE_ClientsAllowCBOR:   'true'
      KUBE_FEATURE_ClientsPreferCBOR:  'true'

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer

Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[dotdc]

Can you remove empty lines in the template?
Otherwise LGTM.

[liangyuanpeng]

Can you remove empty lines in the template?
Otherwise LGTM.

updated.