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/LibJS/Bytecode/StringTable.h

@@ -6,7 +6,7 @@
 
 #pragma once
 
-#include <AK/DeprecatedString.h>
+#include <AK/ByteString.h>
 #include <AK/DistinctNumeric.h>
 #include <AK/Vector.h>
 
@@ -21,13 +21,13 @@ class StringTable {
 public:
     StringTable() = default;
 
-    StringTableIndex insert(DeprecatedString);
-    DeprecatedString const& get(StringTableIndex) const;
+    StringTableIndex insert(ByteString);
+    ByteString const& get(StringTableIndex) const;
     void dump() const;
     bool is_empty() const { return m_strings.is_empty(); }
 
 private:
-    Vector<DeprecatedString> m_strings;
+    Vector<ByteString> m_strings;
 };
 
 }