[bitnami/contour] allow customizing lifecycle hooks for envoy containers

[therealak12]

Description of the change

Adds a new value to the contour's chart to allow customizing lifecycle hooks in the Envoy and shutdown manager containers.

Benefits

When using hostNetwork: true, the httpGet probe must be customized by adding a Host header or a host field. Obviously, this is not the only benefit of allowing this customization.

Possible drawbacks

Users may set random lifecycle hooks and unintentionally disable or disrupt the shutdown manager functionality.

Additional information

The change is only made on the Envoy deployment template. The daemonset already allows customizing lifecycle hooks for the shutdown manager container but not the Envoy container. Changing the daemonset template makes the chart backward-incompatible.

Checklist

• [X] Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• [X] Variables are documented in the values.yaml and added to the README.md using readme-generator-for-helm
• [X] Title of the pull request follows this pattern [bitnami/<name_of_the_chart>] Descriptive title
• [X] All commits signed off and in agreement of Developer Certificate of Origin (DCO)