[ChromeVox] Convert AutoScrollHandler to TypeScript

AX-Relnotes: n/a.
Bug: b/267329383
Change-Id: Icd9c67ad4c5ee29723e8c710dfe9328502a36992
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5739135


Auto-Submit: Anastasia Helfinstein <anastasi@google.com>
Reviewed-by: Amanda Lin Dietz <aldietz@google.com>
Commit-Queue: Anastasia Helfinstein <anastasi@google.com>
Cr-Commit-Position: refs/heads/main@{#1343868}