unpack_bootimg: adding BootImageInfoFormatter am: 39b2d4fac9 am: 7a123c184c am: 94f84070e3

Original change: https://android-review.googlesource.com/c/platform/system/tools/mkbootimg/+/1687707

Change-Id: I3cf372facd7f4835a16a00b9a6c3a42c024ff284