Refactor modals in XWikiUserNotificationsSheet

Currently, we create two modals for each notification preference created in the notification center, this can lead to some latency on the client side due to a bigger DOM.

As those modals are pretty much the same (except that they all have a different ID), we could try to create two generic modals for every notification preference.

For reference :
First modal : https://github.com/xwiki/xwiki-platform/blob/337a24e1820d6c226830394f7a6f419153071713/xwiki-platform-core/xwiki-platform-notifications/xwiki-platform-notifications-ui/src/main/resources/XWiki/Notifications/Code/XWikiUserNotificationsSheet.xml#L256

Second modal : https://github.com/xwiki/xwiki-platform/blob/337a24e1820d6c226830394f7a6f419153071713/xwiki-platform-core/xwiki-platform-notifications/xwiki-platform-notifications-ui/src/main/resources/XWiki/Notifications/Code/XWikiUserNotificationsSheet.xml#L291