Everywhere: Rename {Deprecated => Byte}String

This commit un-deprecates DeprecatedString, and repurposes it as a byte
string.
As the null state has already been removed, there are no other
particularly hairy blockers in repurposing this type as a byte string
(what it _really_ is).

This commit is auto-generated:
  $ xs=$(ack -l \bDeprecatedString\b\|deprecated_string AK Userland \
    Meta Ports Ladybird Tests Kernel)
  $ perl -pie 's/\bDeprecatedString\b/ByteString/g;
    s/deprecated_string/byte_string/g' $xs
  $ clang-format --style=file -i \
    $(git diff --name-only | grep \.cpp\|\.h)
  $ gn format $(git ls-files '*.gn' '*.gni')

Userland/Libraries/LibCore/Directory.cpp

@@ -53,7 +53,7 @@ ErrorOr<Directory> Directory::adopt_fd(int fd, LexicalPath path)
     return Directory { fd, move(path) };
 }
 
-ErrorOr<Directory> Directory::create(DeprecatedString path, CreateDirectories create_directories, mode_t creation_mode)
+ErrorOr<Directory> Directory::create(ByteString path, CreateDirectories create_directories, mode_t creation_mode)
 {
     return create(LexicalPath { move(path) }, create_directories, creation_mode);
 }