Add a feature for mapping real files into the symbolic filesystem

[Boyan-MILANOV]

Maat's loader has some code to map a real file from the host computer to the virtual symbolic filesystem:

maat/src/loader/loader_lief_elf.cpp

Lines 604 to 613 in edd4e71

	engine->env->fs.create_file(lib_fs_path, true);
	env::physical_file_t pfile = engine->env->fs.get_file(lib_fs_path);
	if (pfile == nullptr) {
	throw loader_exception(
	Fmt() << "Error getting file in emulated filesystem: "
	<< lib_fs_path >>
	Fmt::to_str);
	}
	addr_t offset = 0;
	pfile->copy_real_file(lib_path);

We should definitely allow to do this automatically from a simple method, as part of the FileSystem API. For example FileSystem::add_real_file(/path/to/real/file, /path/in/virtual/fs). The method must also be exposed in the python bindings.

This feature is required by #93 (comment)

[Boyan-MILANOV]

Fixed by #116 in the dev-next branch