AImageDecoder: Add a fuzz target

Bug: 142252770
Bug: 169137236
Bug: 169139756
Test: This (fuzzer)

Use the bytes to create an image file and decode it.

To run:

$ SANITIZE_TARGET=hwaddress make imagedecoder_fuzzer
$ adb root
$ adb sync data
$ adb shell /data/fuzz/arm64/imagedecoder_fuzzer/imagedecoder_fuzzer

Call startThreadPool() to support HEIF. Otherwise HEIF decodes may time
out on binder IPC calls. This is similar to a fix for skia_dm in
https://skia-review.googlesource.com/c/skia/+/108141.

Change-Id: I434730a74c5ff97437526065c41af3f54fae3335