[fir][NFC] Move parser/printer for fir.global_len

[clementval]

Summary

Move parser and printer to the .cpp file.

Follow up to https://reviews.llvm.org/D110626.

This patch is part of the upstreaming effort from fir-dev branch.

flang/include/flang/Optimizer/Dialect/FIROps.td

```mlir
         %1 = fir.undefined : !fir.type<t(len1:i32)>
         return %1 : !fir.type<t(len1:i32)>
       }
     ```
   }];
 
   let arguments = (ins StrAttr:$lenparam, APIntAttr:$intval);
 
-  let parser = [{
-    llvm::StringRef fieldName;
-    if (failed(parser.parseOptionalKeyword(&fieldName))) {
-      mlir::StringAttr fieldAttr;
-      if (parser.parseAttribute(fieldAttr, lenParamAttrName(),
-                                result.attributes))
-        return mlir::failure();
-    } else {
-      result.addAttribute(lenParamAttrName(),
-          parser.getBuilder().getStringAttr(fieldName));
-    }
-    mlir::IntegerAttr constant;
-    if (parser.parseComma() ||
-        parser.parseAttribute(constant, intAttrName(), result.attributes))
-      return mlir::failure();
-    return mlir::success();
-  }];
+  let parser = "return parseGlobalLenOp(parser, result);";
 
-  let printer = [{
-    p << ' ' << (*this)->getAttr(lenParamAttrName())
-      << ", " << (*this)->getAttr(intAttrName());
-  }];
+  let printer = "::print(p, *this);";
 
   let extraClassDeclaration = [{
     static constexpr llvm::StringRef lenParamAttrName() { return "lenparam"; }
     static constexpr llvm::StringRef intAttrName() { return "intval"; }
   }];
 }
 
 def ImplicitFirTerminator : SingleBlockImplicitTerminator<"FirEndOp">;

flang/lib/Optimizer/Dialect/FIROps.cpp

static mlir::ArrayAttr collectAsAttributes(mlir::MLIRContext *ctxt,
   llvm::SmallVector<mlir::Attribute> attrs;
   for (auto v : inds)
     appendAsAttribute<AllowFields>(attrs, v);
   assert(!attrs.empty());
   return mlir::ArrayAttr::get(ctxt, attrs);
 }
 
 //===----------------------------------------------------------------------===//
+// GlobalLenOp
+//===----------------------------------------------------------------------===//
+
+static mlir::ParseResult parseGlobalLenOp(mlir::OpAsmParser &parser,
+                                          mlir::OperationState &result) {
+  llvm::StringRef fieldName;
+  if (failed(parser.parseOptionalKeyword(&fieldName))) {
+    mlir::StringAttr fieldAttr;
+    if (parser.parseAttribute(fieldAttr, fir::GlobalLenOp::lenParamAttrName(),
+                              result.attributes))
+      return mlir::failure();
+  } else {
+    result.addAttribute(fir::GlobalLenOp::lenParamAttrName(),
+                        parser.getBuilder().getStringAttr(fieldName));
+  }
+  mlir::IntegerAttr constant;
+  if (parser.parseComma() ||
+      parser.parseAttribute(constant, fir::GlobalLenOp::intAttrName(),
+                            result.attributes))
+    return mlir::failure();
+  return mlir::success();
+}
+
+static void print(mlir::OpAsmPrinter &p, fir::GlobalLenOp &op) {
+  p << ' ' << op.getOperation()->getAttr(fir::GlobalLenOp::lenParamAttrName())
+    << ", " << op.getOperation()->getAttr(fir::GlobalLenOp::intAttrName());
+}
+
+//===----------------------------------------------------------------------===//
 // ExtractValueOp
 //===----------------------------------------------------------------------===//
 
 void fir::ExtractValueOp::build(mlir::OpBuilder &builder,
                                 OperationState &result, mlir::Type resTy,
                                 mlir::Value aggVal,
                                 llvm::ArrayRef<mlir::Value> inds) {
   auto aa = collectAsAttributes<>(builder.getContext(), result, inds);