Parameterless MethodBody Constructors

[Washi1337]

Removes owner parameters from CilMethodBody, NativeMethodBody and UnresolvedMethodBody, allowing them to be used in C# object initializer syntax. Assigning to MethodDefinition::MethodBody may now throw an ArgumentException when the body was already assigned to another method body.

Before:

MethodDefinition method = ...;
var body = new CilMethodBody(owner: method)
{
   Instruction = { ... }
};
method.CilMethodBody = body;

After:

MethodDefinition method = ...;
method.CilMethodBody = new CilMethodBody
{
   Instruction = { ... }
};