Refactoring the translation of execve() and fixing the handling of shebang

[imlk0]

This PR contains two main parts:

• Refactoring the translation of execve()

  • The old execve() translation function does not implement recursive parsing of the interpreter, which means that the interpreter of a script file can not be a script file, resulting in a limitation. This PR fixed that problem.
  • The previous process of loading executable files is less extensible. For this reason, I split the load function into load_elf() and load_script().

• Fixing the handling of shebang

  • As mentioned in Shebang parsing doesn't work for binary files #8 (comment), the argument in the shebang line of script file are not handled correctly. This PR rewrites the parsing of script files.
  • Added integration test for loading script file.