[MLIR] Add getI2Type/getI4Type/getI16type to `OpBuilder`

[pecopty]

Summary

Declaration and implementation of the functions getI2/4/16Type() are added to Builders.h/cpp respectively.

[hgreving]

Ok to me for the convenience method but please get one more opinion

mlir/include/mlir/IR/Builders.h

public:
   FloatType getF32Type();
   FloatType getF64Type();
   FloatType getF80Type();
   FloatType getF128Type();
 
   IndexType getIndexType();
 
   IntegerType getI1Type();
+  IntegerType getI2Type();
+  IntegerType getI4Type();
   IntegerType getI8Type();
+  IntegerType getI16Type();
   IntegerType getI32Type();
   IntegerType getI64Type();
   IntegerType getIntegerType(unsigned width);
   IntegerType getIntegerType(unsigned width, bool isSigned);
   FunctionType getFunctionType(TypeRange inputs, TypeRange results);
   TupleType getTupleType(TypeRange elementTypes);
   NoneType getNoneType();
 

mlir/lib/IR/Builders.cpp

 FloatType Builder::getF80Type() { return FloatType::getF80(context); }
 
 FloatType Builder::getF128Type() { return FloatType::getF128(context); }
 
 IndexType Builder::getIndexType() { return IndexType::get(context); }
 
 IntegerType Builder::getI1Type() { return IntegerType::get(context, 1); }
 
+IntegerType Builder::getI2Type() { return IntegerType::get(context, 2); }
+
+IntegerType Builder::getI4Type() { return IntegerType::get(context, 4); }
+
 IntegerType Builder::getI8Type() { return IntegerType::get(context, 8); }
 
+IntegerType Builder::getI16Type() { return IntegerType::get(context, 16); }
+
 IntegerType Builder::getI32Type() { return IntegerType::get(context, 32); }
 
 IntegerType Builder::getI64Type() { return IntegerType::get(context, 64); }
 
 IntegerType Builder::getIntegerType(unsigned width) {
   return IntegerType::get(context, width);
 }