fix files left pane doesn't scroll when needed
fix files left pane doesn't scroll when needed

call scrollIntoView on tree node in setFocus

test plan
- navigate to a files page
- tab until the left pane is focused
- use the arrow keys to move down the file tree until you move past the
bottom of the viewable area
- view should adjust to include the now focused area

fixes CNVS-26568

Change-Id: Ic47df1e8d465c5376e91beabdfb9a91867dc84b3
Reviewed-on: https://gerrit.instructure.com/74170
Reviewed-by: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>
Tested-by: Jenkins
QA-Review: Deepeeca Soundarrajan <5bcd4b623f00b7fc2942cd1c65c245b30a48a61f@instructure.com>
Product-Review: Aaron Cannon <25919c673621c006b735dcd5a28df63325948e2b@instructure.com>

sfu/canvas-lms,fronteerio/canvas-lms,matematikk-mooc/canvas-lms,dgynn/canvas-lms,dgynn/canvas-lms,matematikk-mooc/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,djbender/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,SwinburneOnline/canvas-lms,fronteerio/canvas-lms,fronteerio/canvas-lms,sfu/canvas-lms,roxolan/canvas-lms,instructure/canvas-lms,roxolan/canvas-lms,venturehive/canvas-lms,HotChalk/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,HotChalk/canvas-lms,matematikk-mooc/canvas-lms,dgynn/canvas-lms,SwinburneOnline/canvas-lms,HotChalk/canvas-lms,grahamb/canvas-lms,instructure/canvas-lms,venturehive/canvas-lms,dgynn/canvas-lms,grahamb/canvas-lms,roxolan/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,SwinburneOnline/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,SwinburneOnline/canvas-lms,roxolan/canvas-lms,matematikk-mooc/canvas-lms,grahamb/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,venturehive/canvas-lms,instructure/canvas-lms,fronteerio/canvas-lms