Support /product partition

This CL adds the following build flags to support building product partition
from Android build system.
- BOARD_AVB_PRODUCT_ADD_HASHTREE_FOOTER_ARGS
- BOARD_AVB_PRODUCT_KEY_PATH
- BOARD_AVB_PRODUCT_ALGORITHM
- BOARD_AVB_PRODUCT_ROLLBACK_INDEX_LOCATION
- BOARD_PREBUILT_PRODUCTIMAGE
- BOARD_PRODUCTIMAGE_EXTFS_INODE_COUNT
- BOARD_PRODUCTIMAGE_FILE_SYSTEM_TYPE
- BOARD_PRODUCTIMAGE_PARTITION_SIZE
- BOARD_PRODUCTIMAGE_SQUASHFS_BLOCK_SIZE
- BOARD_PRODUCTIMAGE_SQUASHFS_COMPRESSOR
- BOARD_PRODUCTIMAGE_SQUASHFS_COMPRESSOR_OPT
- BOARD_PRODUCTIMAGE_SQUASHFS_DISABLE_4K_ALIGN
- BOARD_USES_PRODUCTIMAGE
- LOCAL_PRODUCT_MODULE
- PRODUCT_FOOTER_ARGS
- PRODUCT_PRODUCT_BASE_FS_PATH
- PRODUCT_PRODUCT_VERITY_PARTITION
- TARGET_COPY_OUT_PRODUCT
- TARGET_OUT_PRODUCT*

And PRODUCT_PRODUCT_PROPERTIES is added to save product-specific
properties in /product/build.prop.

Bug: 64195575
Test: succeeded building product.img with BOARD_PRODUCTIMAGE_PARTITION_SIZE,
BOARD_PRODUCTIMAGE_FILE_SYSTEM_TYPE and PRODUCT_PRODUCT_VERITY_PARTITION.

Change-Id: I774e6a38003734421591e51bed103802ff84f432