fix(ns-ipsec): synchronize disabled state for existing routes in edit tunnel API

[m-dilorenzi]

This pull request makes improvements to the management of route state when editing an IPsec tunnel in the ns.ipsectunnel module. The main focus is on ensuring that the enabled/disabled status of the tunnel is consistently applied to all associated routes.

Route state synchronization:

• Introduced the route_disabled variable to centralize the logic for determining route disabled state based on the tunnel's enabled argument.
• Updated route creation logic to use the new route_disabled variable for setting the disabled state, ensuring consistency.
• Added a loop to synchronize the disabled state across all existing routes linked to the tunnel, using uci_set_if_changed to update only when necessary.

Closes: #1558