This commit adds field initializers to the CFG for non-static constructors. For
example, in
```
class C
{
int Field1 = 0;
int Field2 = Field1 + 1;
int Field3;
public C()
{
Field3 = 2;
}
public C(int i)
{
Field3 = 3;
}
}
```
the initializer expressions `Field1 = 0` and `Field2 = Field1 + 1` are added
to the two constructors, mimicking
```
public C()
{
Field1 = 0;
Field2 = Field1 + 1;
Field3 = 2;
}
```
and
```
public C()
{
Field1 = 0;
Field2 = Field1 + 1;
Field3 = 3;
}
```
respectively. This means that we no longer have to synthesize calls, callables,
parameters, and arguments in the data flow library, so much of the work from
d1755500e4 can be simplified.
