Add 'make fuzz' build rule.

Adds the `make fuzz` build rule. This offers a few features on top of
`make haiku`:
 1. Identifies all fuzz targets through the build system, rather than
 having to maintain a golden file.
 2. Packages now exist in out/soong/ and are packaged on a per-architecture
 basis. Packages also now contain fuzzer seed corpus && dictionary.
 3. This gives us further extension options:
  - Packaging shared libraries for shared library fuzzing.
  - Presubmit tests for fuzzing. Each fuzz target could be made into a
  regression test by adding the crash testcase to the corpus. We can
  also ensure that example_fuzzer finds a bug with an ASan report as a
  presubmit smoke test.

Bug: 141026328
Test: m fuzz && unzip -l out/soong/fuzz-$ARCH.zip

Change-Id: I7aaad616d6b194a3beaf908241a9817df9dfdce1