[DWARFYAML][debug_aranges] Use yaml::Hex64 rather than uint64_t as length. NFC.

It's better to use yaml::Hex64 as length in the tuples of the address
range table.

llvm/include/llvm/ObjectYAML/DWARFYAML.h

@@ -61,7 +61,7 @@ struct Abbrev {
 
 struct ARangeDescriptor {
   llvm::yaml::Hex64 Address;
-  uint64_t Length;
+  yaml::Hex64 Length;
 };
 
 struct ARange {

llvm/test/ObjectYAML/MachO/DWARF-debug_aranges.yaml

@@ -333,7 +333,7 @@ DWARF:
 # CHECK-NEXT:       AddressSize:         0x08
 # CHECK-NEXT:       Descriptors:
 # CHECK-NEXT:         - Address: 0x0000000100000F50
-# CHECK-NEXT:           Length:  52
+# CHECK-NEXT:           Length:  0x0000000000000034
 
 ## b) Test that if the "debug_aranges" entry is empty, yaml2macho will only emit the
 ## section header.