💥🐛Change DataMember ordering to 1-indexed (#1360)

Related #1200
Fixes #1356

Apparently, protobuf-net does not support 0-indexed order values.

- Change `DataMember` explicit order from 0-indexed to 1-indexed

Some investigation indicates that the actual order value is not important, only the relative ordering:
#1356 (comment)

- WCF should tolerate this, according to its docs. #1356 (comment)
- Binary formatters hopefully only care about relative ordering and thus still compatible?
	- Protobuf-net, it never worked and should be OK
	- [BinaryFormatter](https://learn.microsoft.com/en-us/dotnet/api/system.runtime.serialization.formatters.binary.binaryformatter?view=net-8.0) is obsolete and generally not recommended for years, so hopefully no users are affected
	- A bunch of others exist too, haven't looked into how they handle this
- XML/JSON serializers should tolerate any order, can't imagine it breaking these?

CodeGen/Generators/UnitsNetGen/QuantityGenerator.cs

@@ -82,13 +82,13 @@ namespace UnitsNet
         /// <summary>
         ///     The numeric value this quantity was constructed with.
         /// </summary>
-        [DataMember(Name = ""Value"", Order = 0)]
+        [DataMember(Name = ""Value"", Order = 1)]
         private readonly {_quantity.ValueType} _value;
 
         /// <summary>
         ///     The unit this quantity was constructed with.
         /// </summary>
-        [DataMember(Name = ""Unit"", Order = 1)]
+        [DataMember(Name = ""Unit"", Order = 2)]
         private readonly {_unitEnumName}? _unit;
 ");
             GenerateStaticConstructor();