[bitnami/common] Add common.tplvalues.merge-overwrite helper

[maxnitze]

Description of the change

Adding a new helper to the Bitnami common chart. This helper uses the sprig function mergeOverwrite to merge multiple dictionaries into one.

Benefits

• merging two or more dicts with precedence consistent with mergeOverwrite
  • precedence "from right to left"
• fixes issues, where it is not possible to overwrite "truthy" values with "falsy" values, even when the "falsy" values should have precedence according to the docs
  • for more see [bitnami/common] common.tplvalues.merge ignores precedence on falsy values #29566 and Merge function does not overwrite if new value is falsy Masterminds/sprig#134

Possible drawbacks

None

Applicable issues

• needed for [bitnami/argo-cd] Add native support for ConfigManagementPlugins #27628
• fixes [bitnami/common] common.tplvalues.merge ignores precedence on falsy values #29566
• Masterminds/sprig issue for reference Merge function does not overwrite if new value is falsy Masterminds/sprig#134

Additional information

%

Checklist

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

[juan131]

Thanks so much for this great contribution! Take a look at my comments