app: aboot: Support for fastboot enhancements
app: aboot: Support for fastboot enhancements

Enhance fastboot to support new functionalities:
- fastboot getvar partition-size:<partition_name>: Return the
  size of the partition in bytes
- fastboot getvar partition-type:<partition_name>: Return the
  type of the partition (ext4/vfat)
- fastboot getvar max-download-size: Return the maximum size of
  the image that can be downloaded using fastboot
- Add fastboot preflash command support

Change-Id: Ic612d822129c996ddb6697046b4865c54317d52d

mozilla-b2g/kernel_lk,M1cha/android_bootable_bootloader_lk,jsr-d10/android_bootable_bootloader_lk,Redmi-dev/android_bootable_lk,M1cha/android_bootable_bootloader_lk,lg-devs/g2-bootloader,chirayudesai/android_bootable_bootloader_lk,efidroid/lk,jsr-d10/android_bootable_bootloader_lk,idor/dk50-bootable_bootloader_lk,M1cha/lktris,jbott/lk_gee,Foxda-Tech/polaris-bootable-bootloader-lk,M1cha/android_bootable_bootloader_lk,M1cha/lktris,Redmi-dev/android_bootable_lk,jbott/lk_gee,CanarySolutions/little-kernel,Foxda-Tech/polaris-bootable-bootloader-lk,efidroid/lk,t2m-foxfone/android_kernel_lk,Foxda-Tech/argo8-bootable-bootloader-lk,jbott/lk_gee,efidroid/lk,t2m-foxfone/kernel_lk,t2m-foxfone/android_kernel_lk,t2m-foxfone/kernel_lk,jbott/lk_gee,chirayudesai/android_bootable_bootloader_lk,jsr-d10/android_bootable_bootloader_lk,mozilla-b2g/kernel_lk,efidroid/lk,t2m-foxfone/android_kernel_lk,lg-devs/g2-bootloader,detule/lk-g2-spr,Foxda-Tech/argo8-bootable-bootloader-lk,t2m-foxfone/android_kernel_lk,jsr-d10/android_bootable_bootloader_lk,chirayudesai/android_bootable_bootloader_lk,t2m-foxfone/kernel_lk,efidroid/lk,idor/dk50-bootable_bootloader_lk,CanarySolutions/little-kernel,M1cha/android_bootable_bootloader_lk,mozilla-b2g/fairphone2_kernel_lk,chirayudesai/android_bootable_bootloader_lk,mozilla-b2g/fairphone2_kernel_lk,CanarySolutions/little-kernel,t2m-foxfone/android_kernel_lk,jsr-d10/android_bootable_bootloader_lk,mozilla-b2g/kernel_lk,jbott/lk_gee,M1cha/lktris,mozilla-b2g/fairphone2_kernel_lk,mozilla-b2g/fairphone2_kernel_lk,M1cha/lktris,M1cha/android_bootable_bootloader_lk,Foxda-Tech/argo8-bootable-bootloader-lk,t2m-foxfone/kernel_lk,Foxda-Tech/argo8-bootable-bootloader-lk,mozilla-b2g/kernel_lk,Redmi-dev/android_bootable_lk,idor/dk50-bootable_bootloader_lk,detule/lk-g2-spr,mozilla-b2g/fairphone2_kernel_lk,Redmi-dev/android_bootable_lk,CanarySolutions/little-kernel,Foxda-Tech/polaris-bootable-bootloader-lk,lg-devs/g2-bootloader,mozilla-b2g/kernel_lk,Foxda-Tech/polaris-bootable-bootloader-lk,idor/dk50-bootable_bootloader_lk,lg-devs/g2-bootloader,detule/lk-g2-spr,Foxda-Tech/argo8-bootable-bootloader-lk,detule/lk-g2-spr,detule/lk-g2-spr,Redmi-dev/android_bootable_lk,t2m-foxfone/kernel_lk,chirayudesai/android_bootable_bootloader_lk,M1cha/lktris,lg-devs/g2-bootloader,M1cha/android_bootable_bootloader_lk,CanarySolutions/little-kernel,Foxda-Tech/polaris-bootable-bootloader-lk,idor/dk50-bootable_bootloader_lk