message: Remove byte counting from SourceManager [NFC]
  Summary:
  Similar to what we did in D50681, we now stop manually byte counting here
  in the SourceManager.
  Reviewers: #lldb, JDevlieghere
  Subscribers: JDevlieghere, abidh, lldb-commits
diff: @@ -158,7 +158,9 @@ size_t SourceManager::DisplaySourceLinesWithLineNumbersUsingLastFile(
  const SymbolContextList *bp_locs) {
  if (count == 0)
  return 0;
  - size_t return_value = 0;
  +
  + Stream::ByteDelta delta(*s);
  +
  if (start_line == 0) {
  if (m_last_line != 0 && m_last_line != UINT32_MAX)
  start_line = m_last_line + m_last_count;
  @@ -193,7 +195,6 @@ size_t SourceManager::DisplaySourceLinesWithLineNumbersUsingLastFile(
  ::snprintf(prefix, sizeof(prefix), " ");
  }
  - return_value +=
  s->Printf("%s%2.2s %-4u\t", prefix,
  line == curr_line ? current_line_cstr : "", line);
  @@ -211,21 +212,20 @@ size_t SourceManager::DisplaySourceLinesWithLineNumbersUsingLastFile(
  // Display caret cursor.
  std::string src_line;
  m_last_file_sp->GetLine(line, src_line);
  - return_value += s->Printf(" \t");
  + s->Printf(" \t");
  // Insert a space for every non-tab character in the source line.
  for (size_t i = 0; i + 1 < column && i < src_line.length(); ++i)
  - return_value += s->PutChar(src_line[i] == '\t' ? '\t' : ' ');
  + s->PutChar(src_line[i] == '\t' ? '\t' : ' ');
  // Now add the caret.
  - return_value += s->Printf("^\n");
  + s->Printf("^\n");
  }
  if (this_line_size == 0) {
  m_last_line = UINT32_MAX;
  break;
  - } else
  - return_value += this_line_size;
  }
  }
  - return return_value;
  + }
  + return *delta;
  }
  size_t SourceManager::DisplaySourceLinesWithLineNumbers(
  