Move IO from under the ResourcesManager lock

ApkAssets.isUpToDate() performs IO for many types of assets,
and doing it under a highly contended lock may cause visible
jank.

Given that we don't have to remove the key right at the time of
the lookup, it's fine to move the up-to-date check out of the
lock - if it's not, the function would replace the outdated
asset anyway

Bug: 259941466
Test: build + boot
Change-Id: I8828deadc82180e93bbd9fc34f80a7bd9411d4ad