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/Module.cpp

@@ -17,7 +17,7 @@ namespace JS {
 
 JS_DEFINE_ALLOCATOR(Module);
 
-Module::Module(Realm& realm, DeprecatedString filename, Script::HostDefined* host_defined)
+Module::Module(Realm& realm, ByteString filename, Script::HostDefined* host_defined)
     : m_realm(realm)
     , m_host_defined(host_defined)
     , m_filename(move(filename))