Add a subfolder grouping option to each folder

[Rafee-M]

Checklist

• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I have read the FAQ and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• This issue contains only one feature request.
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Is your feature request related to a problem? Please describe.
Currently you can enable subfolder grouping on the main screen i.e for all folders

Describe the solution you'd like
If that option is added for each individual folders it would be useful if the user wants to enable group subfolders for specific folders only.

Additional context

Option to be added (from Main Screen > Change view type)

Target menu for new option (located at any folder > Change view type)

[sn0ot]

I came to also request that. An example use case could be, for example:

Before feature:

• Have 5 folders for different travel destinations at top level

After feature:

• Have one folder on the top level called "Travel" and each of the individual travel folder should be a subfolder.
• I want to stress that organization of pictures should be done without use of "virtual albums or tagging" (not sure if there are technical terms).
  • Virtual Albums or Tagging: In the first approach, where albums are links to pictures without making copies, you can think of it as a form of virtual albums or tagging system.
  • Physical Folders or Hierarchical Organization: In the second approach, where pictures are organized into folders and moved around, it follows a physical or hierarchical organization method. This means that each photo is placed in a specific folder or directory, and it cannot exist in multiple locations without creating copies

Considerations:
This feature would have to be applied at the scope of a folder (as opposed to a global toggle). We probably don't want a global toggle because some camera apps save pictures into DCIM/<month picture was taken>.

An elegant way I can see to implement this (at a high level) is to have a user populate a list (similar mechanism to the manage included folders and manage excluded folders that exists now). And all folders that appear in that list, they will be rendered in the gallery app. We probably also want the ability to include all subfolders (/storage/emulated/0/foo/*) so the user doesn't have to add each subfolder (unless they wanted to)

[ThreeDeeJay]

It would be nice to be able to search for grouped subfolders without having to ungroup them first, especially since groups reduce the need for search and might even be faster to just scroll through when there's fewer of them.
Perhaps it could also be combined with the "Search all files instead of folders on the main screen" option (or just a separate one) so that search includes both grouped subfolders and files.

Also it might be handy to always show pinned subfolders at the top instead of hidden within their parent group, so that we can have both easy-access folder and the lower priority folders can still remain in their group to reduce clutter.