feat: preserve formatting and comments when updating Helm values file

[kirgene]

Description

This PR enhances the Helm values file update functionality by preserving the original formatting and comments. Previously, updating the file would overwrite manual formatting and comments, which could be problematic for users who rely on these customizations for clarity and maintenance. By retaining inline comments and specific formatting, this change improves the user experience and reduces potential confusion after automated updates.

Additionally, this update refines how image-name and image-tag keys are handled:

• By default, key path in image-name and image-tag creates a nested structure. For example:

  argocd-image-updater.argoproj.io/nginx.helm.image-name: image.name
  argocd-image-updater.argoproj.io/nginx.helm.image-tag: image.tag

  Produces:

  image:
    name: app-name
    tag: v1.0.0

• If a user wants to update Helm values that contain dots, the key path must be quoted (either with double or single quotes):

  argocd-image-updater.argoproj.io/nginx.helm.image-name: '"image.name"'
  argocd-image-updater.argoproj.io/nginx.helm.image-tag: '"image.tag"'

  This will correctly produce:

  image.name: app-name
  image.tag: v1.0.0

These changes ensure greater flexibility and correctness in handling Helm values updates while maintaining user-defined formatting.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.41758% with 16 lines in your changes missing coverage. Please review.

Project coverage is 62.49%. Comparing base (add409e) to head (7f81de7).

Files with missing lines	Patch %	Lines
pkg/argocd/update.go	82.22%	9 Missing and 7 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1039      +/-   ##
==========================================
- Coverage   62.59%   62.49%   -0.10%     
==========================================
  Files          15       15              
  Lines        2259     2293      +34     
==========================================
+ Hits         1414     1433      +19     
- Misses        755      764       +9     
- Partials       90       96       +6     

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