Sorround Helm appVersion with quotes only if it is numeric

What does this MR do and why?

In !166663 (merged) we updated the Helm package presenter to surround the appVersion metadata field with quotes, to better handle numeric values. Unfortunately, this broke the presenter for values with string values.

This refines the quoting logic to apply quoting only for numeric values.

MR acceptance checklist

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Screenshots or screen recordings

NA

How to set up and validate locally

We'll verify that this MR keeps the fix for numeric versions done by !166663 (merged), and fixes the issue for string versions introduced by !166663 (merged)

Preliminaries

We'll need a project (get the project ID), a personal access token with scope set to api, and two helm charts, one with a numeric version (e.g. 4852e004) and one with a string version (e.g. master).

1. Add the bananas repo to helm: helm repo add --username root --password glpat-zzz bananas http://gdk.test:3000/api/v4/projects/7/packages/helm/bananas
2. Create and upload the numericversion package

• helm create numericversion
• edit numericversion/Chart.yaml - change the value of appVersion to 4852e004
• helm package numericversion
• curl --fail --request POST --user <user>:<personal-access-token> --form "chart=@numericversion-0.1.0.tgz" "http://gdk.test:3000/api/v4/projects/<project-id>/packages/helm/api/bananas/charts";

3. Create and upload the stringversion package

• helm create stringversion
• edit stringversion/Chart.yaml - change the value of appVersion to master
• helm package stringversion
• curl --fail --request POST --user <user>:<personal-access-token> --form "chart=@stringversion-0.1.0.tgz" "http://gdk.test:3000/api/v4/projects/<project-id>/packages/helm/api/bananas/charts";

Related to #490699