[IR] Rename comdat noduplicates to comdat nodeduplicate

In the textual format, `noduplicates` means no COMDAT/section group
deduplication is performed. Therefore, if both sets of sections are retained, and
they happen to define strong external symbols with the same names,
there will be a duplicate definition linker error.

In PE/COFF, the selection kind lowers to `IMAGE_COMDAT_SELECT_NODUPLICATES`.
The name describes the corollary instead of the immediate semantics.  The name
can cause confusion to other binary formats (ELF, wasm) which have implemented/
want to implement the "no deduplication" selection kind. Rename it to be clearer.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D106319

lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1132,7 +1132,7 @@ static unsigned getEncodedComdatSelectionKind(const Comdat &C) {
     return bitc::COMDAT_SELECTION_KIND_EXACT_MATCH;
   case Comdat::Largest:
     return bitc::COMDAT_SELECTION_KIND_LARGEST;
-  case Comdat::NoDuplicates:
+  case Comdat::NoDeduplicate:
     return bitc::COMDAT_SELECTION_KIND_NO_DUPLICATES;
   case Comdat::SameSize:
     return bitc::COMDAT_SELECTION_KIND_SAME_SIZE;