Describe the bug

When switching from post editing to template editing, there's a notice that pops up to explain template editing but it disappears quite rapidly. Because this is such a big switch to be making, it seems smart to make this "stickier" and perhaps consider force people to dismiss it upon first switching over. I imagine this will be annoying if you're doing lots of edits back and forth so perhaps it would be good to make it a bit more intelligent ;). I'll leave this to design to think about the implications of.

From @priethor who helped test this: "Also, when switching from the Post editor to the Template Editor, the “Editing template” notification at the bottom was easy to miss on bigger screens."

To reproduce
Steps to reproduce the behavior:

1. Install Gutenberg 9.6+ and a FSE ready theme.
2. Go to Posts > Add New
3. Make some changes to the post > Save Draft or Publish.
4. Use the option to edit the template to switch into template editing mode in the post settings section.
5. See the notice pop up.

Expected behavior

I expect the notice to stick around for longer and/or to be more "in the user's face".

Screenshots

Editor version (please complete the following information):

• WordPress version: 5.6
• Does the website has Gutenberg plugin installed, or is it using the block editor that comes by default? Gutenberg
• If the Gutenberg plugin is installed, which version is it? 9.7.2

Desktop (please complete the following information):

• OS: MacOS
• Browser: Chrome
• Version: 87.0.4280.141