2.0: rewrite in Rust

[Sk7Str1p3]

Why

#918, #789

Approaches:

• App, not script

  For now, disko is bash script calling nix eval, which is launching commands via shell. This produces bad (i mean BAD) tracing, low performance and hard maintenance. Rust implementation will call functions from libraries directly - there are many crates for interacting with various filesystems, partition tables, luks and lvm, etc...

• Direct usage without nix eval

  Same reasons as in first statement. Solution is quite easy - we use Nix only to convert config to JSON or TOML, and use generated config, or even parse nix config directly.

Also, i hope it's easier to implement some features in rust than bash:

• Boot time formatting (Boot time disko formatting #917)
• Gentle partitioning
  • This means it will not just wipe partition, but try to convert it first. For example, MBR can be converted into GPT, ext4 into btrfs and so on. No guaranties on proper convertion without data loss though, user will be warned

Result:

• Better trace
• Faster and flexible partitioning
• Features that would be difficult to implement on bash

@Mic92 @Lassulus