fastboot: show how long extraction takes.

Before:
  extracting android-info.txt (0 MB)...
  extracting boot.img (29 MB)...
  target reported max download size of 536870912 bytes
  archive does not contain 'boot.sig'
  archive does not contain 'boot_other.img'
  archive does not contain 'dtbo.img'
  archive does not contain 'dt.img'
  archive does not contain 'recovery.img'
  extracting system.img (1928 MB)...
  archive does not contain 'system.sig'
  extracting system_other.img (574 MB)...
  archive does not contain 'system.sig'
  archive does not contain 'vbmeta.img'

After:
  extracting android-info.txt (0 MB) to RAM...
  extracting boot.img (29 MB) to disk... took 0.232s
  target reported max download size of 536870912 bytes
  archive does not contain 'boot.sig'
  archive does not contain 'boot_other.img'
  archive does not contain 'dtbo.img'
  archive does not contain 'dt.img'
  archive does not contain 'recovery.img'
  extracting system.img (1928 MB) to disk... took 10.122s
  archive does not contain 'system.sig'
  extracting system_other.img (574 MB) to disk... took 3.424s
  archive does not contain 'system.sig'
  archive does not contain 'vbmeta.img'

Bug: http://b/69128980
Test: ran manually
Change-Id: Ib190d1cc56ad9da06a4f9a9e822f7dad4a9a53b7