Resize state machine: A fix and a question (#2929)

* Store EGFX state before entering resize state machine

At present the EGFX state is destroyed by states WMRZ_EGFX_DELETE_SURFACE
through WRMZ_EGFX_DELETE. This means that at WMRZ_EGFX_INITIALIZE we
cannot distinguish between EGFX not being ever used, and EGFX
having been torn down. Consequently, when running non-GFX, we don't
correctly recover the session.

* Allow multiple reasons for suppress_output

Replaces the single boolean for suppress_output with
a bitmask, to allow output to be suppressed for
more than one reason

* Disable output during resize

* Add states to dynamic resize

Adds states to the dynamic resize state machine so we wait for a
Deactivation-Reactivation sequence to finish before sending pointer
updates, etc.

* suppress module output during the dynamic resize

* Add support for dynamic resize to VNC backend

xrdp_mm needs to be informed when a resize has been performed so that
the resize stte machine can be updsate.

common/xrdp_client_info.h

@@ -199,7 +199,9 @@ struct xrdp_client_info
     int no_orders_supported;
     int use_cache_glyph_v2;
     int rail_enable;
-    int suppress_output;
+    // Mask of reasons why output may be suppressed
+    // (see enum suppress_output_reason)
+    unsigned int suppress_output_mask;
 
     int enable_token_login;
     char domain_user_separator[16];
@@ -227,6 +229,12 @@ enum xrdp_encoder_flags
     KEY_FRAME_REQUESTED                    = 1 << 3
 };
 
+/*
+ * Return true if output is suppressed for a particular reason
+ */
+#define OUTPUT_SUPPRESSED_FOR_REASON(ci,reason) \
+    (((ci)->suppress_output_mask & (unsigned int)reason) != 0)
+
 /* yyyymmdd of last incompatible change to xrdp_client_info */
 /* also used for changes to all the xrdp installed headers */
 #define CLIENT_INFO_CURRENT_VERSION 20230425