internal/frontend: reduce cache TTLs to 10 minutes
internal/frontend: reduce cache TTLs to 10 minutes

Based on recent request patterns, most cache hits (94%) happen within
10 minutes. Lower all cache TTLs to 10 minutes to validate that the
cache hit ratio doesn't change significantly.

For golang/go#44210

Change-Id: Ia59b7059a04215e4fe4424a4a868bc561d490b86
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/290969
Trust: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
Run-TryBot: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>
TryBot-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite