[Sema]Select correct lexical context during template instantiate

This patch wants to fix inline friend decl like
```
template <class F1> int foo(F1 X);
template <int A1> struct A {
  template <class F1> friend int foo(F1 X) { return A1; }
};

template struct A<1>;
int a = foo(1.0);
```

Differential Revision: https://reviews.llvm.org/D149009