shell: use binfmt misc instead of ld preload to detect wasm executable

[btheado]

1. Configure the kernel to enable binfmt_misc
2. Mount binfmt_misc and configure it to use wexec for files starting with \0asm header
3. Remove preload.so
4. Static compile of busybox
5. Remove busybox related .so files

Fixes #178

[btheado]

I wasn't able to determine if all these .so files are only for busybox. Especially this one. What tests should I run for this change?

[progrium]

Hugely glad you took the time to take this on an make a PR, but major changes have made this obsoleted. We use binfmt_misc in Apptron and the eventual alpine bundle, but our built-in shell is going back to a single binary so we dont need to depend on a VM to get a repl.

Thanks again! Hope you keep contributing!