[mlir] Correct 2 places that result in corrupted conversion rollbacks

[tpopp]

Summary

This corrects the last 2 issues caught by tests when causing dialect
conversion rollbacks to occur.

mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp

Value mlir::LLVM::createGlobalString(Location loc, OpBuilder &builder,
   assert(builder.getInsertionBlock() &&
          builder.getInsertionBlock()->getParentOp() &&
          "expected builder to point to a block constrained in an op");
   auto module =
       builder.getInsertionBlock()->getParentOp()->getParentOfType<ModuleOp>();
   assert(module && "builder points to an op outside of a module");
 
   // Create the global at the entry of the module.
-  OpBuilder moduleBuilder(module.getBodyRegion());
+  OpBuilder moduleBuilder(module.getBodyRegion(), builder.getListener());
   MLIRContext *ctx = builder.getContext();
   auto type = LLVM::LLVMArrayType::get(IntegerType::get(ctx, 8), value.size());
   auto global = moduleBuilder.create<LLVM::GlobalOp>(
       loc, type, /*isConstant=*/true, linkage, name,
       builder.getStringAttr(value));
 
   // Get the pointer to the first character in the global string.
   Value globalPtr = builder.create<LLVM::AddressOfOp>(loc, global);

mlir/lib/Transforms/Utils/DialectConversion.cpp

 static void detachNestedAndErase(Operation *op) {
   for (Region &region : op->getRegions()) {
     for (Block &block : region.getBlocks()) {
       while (!block.getOperations().empty())
         block.getOperations().remove(block.getOperations().begin());
       block.dropAllDefinedValueUses();
     }
   }
+  op->dropAllUses();
   op->erase();
 }
 
 void ConversionPatternRewriterImpl::discardRewrites() {
   // Reset any operations that were updated in place.
   for (auto &state : rootUpdates)
     state.resetOperation();