Media views EmbedLink spinner

[afercia]

When inserting an embeddable media with "Insert from URL", the spinner is shown while you're typing. As I see it, shouldn't work this way. The spinner should be shown when you stop typing, the AJAX call fires and you're waiting for a response.
To reproduce:

• edit a post
• Add media > Insert from URL
• remove http:// from the field and slowly type less then 6 characters
• fetching the embed will start just if you type more than 6 characters but this is useful to clearly see what's happening
• for each character you type or remove (each change event), the spinner will be displayed

[wonderboymusic]

A few issues here:

• We don't need 2 spinners
• If the debounce sensitivity isn't the same between the 2 views (Embed and EmbedLink), the change events will overlap, which is why the spinner is showing too often
• EmbedLink should use the same sensitivity as defined by the Embed controller

[wonderboymusic]

In 32462:

When creating an EmbedLink view, don't add a spinner - it already exists in Embed.
Use the value of wp.media.controller.Embed.sensitivity as the sensitivity value for the debounced method in EmbedLink to ensure that the spinner toggles don't stutter or overlap.

Fixes #32036.