The fields of the custom theme need to be re-filled

Issue

When using the look-and-feel.xml file to create a custom theme in Liferay, users observe that when they update the theme and reapply it, the previously entered data in the custom theme fields is lost. This behavior results in the undesirable requirement of re-entering the data each time the theme is changed.
Steps to reproduce:
1. Create a custom theme using the look-and-feel.xml file.
2. This file contains code related to social media sites. Please refer to the following code for better understanding:
```
<setting configurable="true" key="show-footer" type="checkbox" values="true" /> 
<setting configurable="true" key="fb-link" type="text" value=" " /> 
<setting configurable="true" key="insta-link" type="text" value=" " /> 
<setting configurable="true" key="twitter-link" type="text" value=" " />
```
3. Apply this custom theme on the page site.

4. Enter all the details mentioned in the code and publish the site.

5. Now, configure the page site again with Liferay's classic theme and publish this.

6. Again reconfigure the page site with the custom theme.

Observed Behavior: The fields of the custom theme need to be re-filled.
Expected Behavior: The fields of the custom theme should contain the last filled data.

This observed behavior is intended with DXP, and there is no built-in alternative to retain the configured properties in the custom theme fields.
DXP does not currently provide infrastructure to store historical data from theme settings. As a result, when a theme is changed, the old values are lost, and the data must be re-entered.

If users need to keep the custom theme configuration, it is recommended that they keep an external record of the entered data or create a backup of the theme settings before making any modifications.
It's important to note that this behavior only applies to the look-and-feel.xml file in custom themes. Other theme-related configurations might behave differently.