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/Shell/Parser.cpp

@@ -1069,7 +1069,7 @@ AST::MatchEntry Parser::parse_match_entry()
             if (names.is_empty()) {
                 for (auto& name : regex.parser_result.capture_groups)
                     names.append(TRY_OR(
-                        String::from_deprecated_string(name),
+                        String::from_byte_string(name),
                         error = create<AST::SyntaxError>(MUST(String::from_utf8(_error.string_literal())));
                         break;));
             } else {
@@ -1077,7 +1077,7 @@ AST::MatchEntry Parser::parse_match_entry()
                 for (auto& name : regex.parser_result.capture_groups) {
                     if (names.size() <= index) {
                         names.append(TRY_OR(
-                            String::from_deprecated_string(name),
+                            String::from_byte_string(name),
                             error = create<AST::SyntaxError>(MUST(String::from_utf8(_error.string_literal())));
                             break;));
                         continue;