gfxstream: add processPipeInit and connect to IOStream

This adds processPipeInit() and connect() functions
to the IOStream base class.  This will allow for better
abstraction of the pipe streams.

Reviewed-by: Aaron Ruby <aruby@blackberry.com>
Acked-by: Yonggang Luo <luoyonggang@gmail.com>
Acked-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27246>

src/gfxstream/guest/iostream/include/gfxstream/guest/IOStream.h

@@ -50,6 +50,9 @@ public:
         return m_bufsize < len ? len : m_bufsize;
     }
 
+    virtual int connect(const char* serviceName = nullptr) { return 0; }
+    virtual uint64_t processPipeInit() { return 0; }
+
     virtual void *allocBuffer(size_t minSize) = 0;
     virtual int commitBuffer(size_t size) = 0;
     virtual const unsigned char *readFully( void *buf, size_t len) = 0;