managed-by: Add a visual indicator for Proxy page

[cdrage]

Is your feature request related to a problem? Please describe

Follow up from the UX/UI design on: https://github.com/podman-desktop/podman-desktop/issues/14115 there are certain elements that require "label" functionality to be added.

Specifically a "managed-by" label if there are settings which have been modified by our managed-by configuration. For example:

~ $ cat /Library/Application\ Support/io.podman_desktop.PodmanDesktop/default-settings.json
{
  "proxy.http": "http://example.com:8080",
  "proxy.https": "http://example.com:8080",
  "proxy.no": "localhost"
}
~ $ cat /Library/Application\ Support/io.podman_desktop.PodmanDesktop/locked.json
{
	"locked": ["proxy.http", "proxy.https", "proxy.no"]
}

It should then appear in the Proxy page under the text input field, for example:

(pretend it says proxy instead, this is the UI mockup)

Right now, it shows nothing:

Describe the solution you'd like

A visual indicator of the setting be using by managed-by configuration.

Describe alternatives you've considered

No response

Additional context

This all is based on the UI work here:

https://github.com/podman-desktop/podman-desktop/issues/14115#issuecomment-3479853402

There also may be a potential blocker / issue with certain elements not being blocked correct:

https://github.com/podman-desktop/podman-desktop/issues/14624

More discussions here regarding the label:

https://github.com/podman-desktop/podman-desktop/issues/14007

And keep in mind there is also a refresh happening for the Preferences page in case there are changes:

https://github.com/podman-desktop/podman-desktop/issues/13479 re: core form components