feat(cpio): add newc archive creation utility

dracut-cpio is a minimal cpio archive creation utility written in Rust.
It provides support for a minimal set of features needed to create
performant and space-efficient initramfs archives:
- "newc" archive format only
- reproducible; inode numbers, uid/gid and mtime can be explicitly set
- data segment copy-on-write reflinks
  + using Rust io::copy()'s native copy_file_range() support[1]
  + optional archive data segment alignment for optimal reflink use[2]
- hardlink support
- comprehensive tests asserting GNU cpio binary output compatibility

1. Rust io::copy() copy_file_range()
   rust-lang/rust#75272

2. Data segment alignment
   We're bending the newc spec a bit to inject zeros after the file path
   to provide data segment alignment. These zeros are accounted for in
   the namesize, but some applications may only expect a single
   zero-terminator (and 4 byte alignment). GNU cpio and Linux initramfs
   handle this fine as long as PATH_MAX isn't exceeded.

Signed-off-by: David Disseldorp <ddiss@suse.de>

src/dracut-cpio/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "dracut-cpio"
+description = "cpio archive generator for Dracut"
+authors = ["David Disseldorp"]
+license = "GPL-2.0"
+version = "0.1.0"
+edition = "2018"
+
+[dependencies]
+crosvm = { path = "third_party/crosvm" }
+# please avoid adding any more dependencies