Retain YAML formatting when using the Git write-back method

[sa-spag]

Is your feature request related to a problem? Please describe.
When the Image Updater updates a .argocd-source-<appName>.yaml or kustomiztion.yaml file, it does not retain their indentation. For instance, it may generate the following diff:

 apiVersion: kustomize.config.k8s.io/v1beta1
 resources:
-  - some-resource.yaml
+- some-resource.yaml
 images:
...

Describe the solution you'd like
Instead, the Image Updater should retain the existing formatting.

It turns out the issue is pretty common for other projects that edit YAML (see issues linked to kubernetes-sigs/kustomize#3946). Since version 0.11.1, kyaml enables retaining the source file indention (see kubernetes-sigs/kustomize#4043). This feature has been integrated in Flux's Image Automation Controller (see fluxcd/image-automation-controller#366), and I believe we can implement a similar feature for the Image Updater.

Describe alternatives you've considered
None.

Additional context
None.

[nabadger]

Potentially related: #502

[zagr0]

Would be really great to have the original file content retained, and the only replaced parts are changed.
In our scenario when we write back to git helm values file for new tag, all the values become sorted and reformatted.

[chengfang]

Need to check how to implement this in https://github.com/argoproj-labs/argocd-image-updater/blob/master/pkg/argocd/git.go#L338