Add top level and per-mutator traces to soong_build

- Top-level trace for all soong_build runs
  - Includes adding Peek() to OncePer because not all soong_build
    invocations have GenerateBuildActions run.
- A trace per mutator invocation

Test: m && build/bazel/scripts/print_analysis_metrics.py
Change-Id: Ief5c04630484fb38ec7e3757de45c7dc294d3b3c