btrfs-progs: convert: Add larger device support

btrfs-progs: convert: Add larger device support

With larger file system (in this case its 22TB), ext2fs_open() returns
EXT2_ET_CANT_USE_LEGACY_BITMAPS error message with
ext2fs_read_block_bitmap().

To overcome this issue,
(a) we need pass EXT2_FLAG_64BITS flag with ext2fs_open.
(b) use 64-bit functions like ext2fs_get_block_bitmap_range2,
    ext2fs_inode_data_blocks2,ext2fs_read_ext_attr2
(c) use 64bit types with btrfs_convert_context fields

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=194795
Signed-off-by: Lakshmipathi.G <lakshmipathi.g@giis.co.in>
Signed-off-by: David Sterba <dsterba@suse.com>