unpack_bootimg: adding BootImageInfoFormatter

Similar to VendorBootImageInfoFormatter, adding a
BootImageInfoFormatter to separate the boot image
parsing logic and output info logic.

Bug: 174443192
Test: atest --host mkbootimg_test
Change-Id: Ie82b6c7281cd438dde7b71ee455e5a3f856f3888
1 file changed