Feature: Updated the design for Dual Pane mode

[0x5bfa]

TBA in the next release officially.

• Remove accent color on the bottom for the active pane to display
• Use shadow and focus background only for the active pane

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. Open the one more pane
3. Open InfoPane
4. Make window smaller and see InfoPane at the bottom

Screenshots

[0x5bfa]

I moved background/borderbrush to each user control's Grid to remove unneeded xaml tree (like you did in #7824). Should I separate changes?

[yaira2]

I moved background/borderbrush to each user control's Grid to remove unneeded xaml tree (like you did in #7824). Should I separate changes?

I think it'll be easier for future reference if it's separate.

[yaira2]

Nice work on the shadows!

[yaira2]

We should make sure to test this with Column View

[XTorLukas]

How about instead of changing the shadow, which isn't as pronounced, you use the pane selector.

003524.mp4

[yaira2]

@XTorLukas thank you for your feedback, additional design work will take place in a second PR.

[yaira2]

LGTM