[fidlcat] Fix issue with interface vector resizing.

When the number of interfaces grows, the vector containing the interfaces
grows with it.  This involves the interface being moved.

When you generate an interface for the first time, each interface method is
given a pointer to the enclosing interface.

When the interface vector is resized, the interface method's pointer is
dangling.

This CL fixes the issue in two ways:

- The move constructor for the interface now creates an updated interface
method instead of reusing the old one.

- Interface vector initialization now reserves enough space for all of the
interfaces, so that moves will no longer be necessary.

Change-Id: Ifa4c51f21bb3dc194695d5af5029a46b862ae907