[Optimization] Add cache header to cache images in the browser and CloudFront

[tihuan]

Context:
Currently deep zoom assets aren't cached in the browser, so the browser would still request for the assets even when it already got it

DoD:

1. Update CloudFront cache header to tell the browser to cache the images for at least an hour

Example:

Header Name: Cache-Control
Header Value: public, max-age=3600

In dev Cloudfront:

[tihuan]

@ebezzi I see that staging spatial-deep-zoom cache behavior currently uses Cache Policy CachingOptimized. Can we add Cache-Control: public and max-age: 3600 on it, or do we need to create a new policy to do that?

Thank you!

[tihuan]

Bumping this to p0, since the zooming experience is significantly better with browser caching enabled

[tihuan]

Still not cached