image: add support for EROFS rootfs image generation

image: add support for EROFS rootfs image generation

Add support for generating EROFS rootfs images.

The EROFS filesystem can offer competitive I/O performance while
minimizing final image size when using the MicroLZMA compressor.

Target platform: linux-x86_generic (target-i386_pentium4_musl)

Filesystem     Image Size
=============  ==========
root.erofs     4882432
root.ext4      109051904
root.squashfs  4903302

Co-Developed-by: Gao Xiang <[email protected]>
Signed-off-by: Gao Xiang <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/19244
Signed-off-by: Christian Marangi <[email protected]>