[TI removal] Remove `TerminatorInst` from BasicBlockUtils.h

This requires updating a number of .cpp files to adapt to the new API.
I've just systematically updated all uses of `TerminatorInst` within
these files te `Instruction` so thta I won't have to touch them again in
the future.

llvm-svn: 344498
diff --git a/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp b/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp
index 261ab87..4db5791 100644
--- a/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp
+++ b/llvm/lib/Transforms/Utils/CallPromotionUtils.cpp
@@ -270,8 +270,8 @@
   // Create an if-then-else structure. The original instruction is moved into
   // the "else" block, and a clone of the original instruction is placed in the
   // "then" block.
-  TerminatorInst *ThenTerm = nullptr;
-  TerminatorInst *ElseTerm = nullptr;
+  Instruction *ThenTerm = nullptr;
+  Instruction *ElseTerm = nullptr;
   SplitBlockAndInsertIfThenElse(Cond, CS.getInstruction(), &ThenTerm, &ElseTerm,
                                 BranchWeights);
   BasicBlock *ThenBlock = ThenTerm->getParent();