Code Quality: Introduce flexible pane generation 1

[0x5bfa]

Summary

This is the stage 1.

1. Refactor around the pane holder page (here)
2. Introduce the generation service

Resolved / Related Issues

To prevent extra work, all changes to the Files codebase must link to an approved issue marked as Ready to build. Please insert the issue number following the hashtag with the issue number that this Pull Request resolves.

• Related #11955

Steps used to test these changes

Stability is a top priority for Files and all changes are required to go through testing before being merged into the repo. Please include a list of steps that you used to test this PR.

1. Open Files app
2. If opens with no crash very good