introduce extraInitContainers to helm chart

New extraInitContainers configuration added.
It allows to pass template with a list of containers to execute before
main code-server container started. Main container will only start when
all init containers are  completed (exited with 0 code).

 Additionally changes the way extraContainers is used - instead of
 toYaml use tpl, because this allows to
 reference any values from extraContainers string.

CHANGELOG.md

@@ -3,6 +3,7 @@
 # Changelog
 
 - [Changelog](#changelog)
+  - [Next Version](#next-version)
   - [3.10.1](#3101)
     - [Bug Fixes](#bug-fixes)
     - [Documentation](#documentation)
@@ -51,6 +52,15 @@ VS Code v0.00.0
 
 -->
 
+## Next Version
+
+VS Code v1.56.1
+
+### New Features
+
+- feat: supported `extraInitContainers` in helm chart values
+- feat: changed `extraContainers` to support templating in helm chart
+
 ## 3.10.1
 
 VS Code v1.56.1