Allow extensionServices to be specified

[wasurerarenai]

Similar to #1495 (which didn't support talenv.sops.yaml envsubst), this adds further support for budimanjojo/talhelper#431. With talenv envsubst, secrets can be encrypted, and automatically referenced when talhelper genconfig is ran. This patch adds support for talhelper's extensionServices inclusions.

extraManifests is still useful for adding manifests like v1.7's WatchdogTimerConfig.

Example config.yaml

bootstrap_node_inventory:
  - name: node1
...
    extension_services:
      - name: nut-client
        configFiles:
          - content: MONITOR ${upsmonUpsName}@${upsmonHost}:${upsmonPort} 1 ${upsmonUser} ${upsmonPasswd} slave
            mountPath: /usr/local/etc/nut/upsmon.conf
        environment:
          - UPS_NAME=ups

Results in talconfig.yaml

nodes:
  - hostname: "node1"
...
    extensionServices:
      - name: nut-client
        configFiles:
          - content: |-
              MONITOR ${upsmonUpsName}@${upsmonHost}:${upsmonPort} 1 ${upsmonUser} ${upsmonPasswd} slave
            mountPath: /usr/local/etc/nut/upsmon.conf
        environment:
          - UPS_NAME=ups

When supplied with the talenv.sops.yaml contents:

upsmonHost: 192.168.1.10
upsmonPasswd: password
upsmonPort: 3493
upsmonUpsName: ups
upsmonUser: username

Renders clusterconfig files with:

version: v1alpha1
...
  network:
    hostname: node1
...
  allowSchedulingOnControlPlanes: true
---
apiVersion: v1alpha1
kind: ExtensionServiceConfig
name: nut-client
configFiles:
  - content: MONITOR ups@192.168.1.10:3493 1 username password slave
    mountPath: /usr/local/etc/nut/upsmon.conf
environment:
  - UPS_NAME=ups