Add helm-unittest tests for init containers:
- No init containers by default
- extraInitContainers support (single and multiple)
- Full container spec preservation (command, args, volumeMounts, securityContext)
- Backward compatibility with deprecated initContainers parameter
- Merging of initContainers and extraInitContainers
- Correct ordering when both are specified
Add NOTES.txt with init containers information:
- Show count of configured init containers
- Deprecation warning when old initContainers parameter is used
- Migration guidance to extraInitContainers
This fixes the critical bug where extraInitContainers didn't work and
provides clear migration path from deprecated initContainers.
Co-Authored-By: Claude <noreply@anthropic.com>
Signed-off-by: Aleksei Sviridkin <f@lex.la>
