Revert "Rename llvm::array_lengthof into llvm::size to match std::size from C++17"

This reverts commit ef82063207.

- It conflicts with the existing llvm::size in STLExtras, which will now
  never be called.
- Calling it without llvm:: breaks C++17 compat

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

@@ -574,7 +574,7 @@ bool ObjectFilePECOFF::ParseSectionHeaders(
 }
 
 llvm::StringRef ObjectFilePECOFF::GetSectionName(const section_header_t &sect) {
-  llvm::StringRef hdr_name(sect.name, llvm::size(sect.name));
+  llvm::StringRef hdr_name(sect.name, llvm::array_lengthof(sect.name));
   hdr_name = hdr_name.split('\0').first;
   if (hdr_name.consume_front("/")) {
     lldb::offset_t stroff;