[power] Restructure power framework benchmarks

Move power framework benchmarks and end-to-end tests into
src/power/bench/power_framework

Change-Id: I4e2ee592be7253e5a39b716c4201be0322f1a2f8
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1602311
Reviewed-by: Onath Dillinger <claridge@google.com>
Commit-Queue: Didi She <didis@google.com>
Reviewed-by: Aaron Wood <aaronwood@google.com>