[iOS] Updates download_manager_state_view using symbols

This CL rewrites download_manager_state_view to make it clearer and
SF symbol friendly.

Bug: 1315544
Change-Id: I96ab30e5ea557eeb229f3c808be17113cdbda5c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3627634


Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Cr-Commit-Position: refs/heads/main@{#999807}