minor cleanup proposal (#4169)

* MESHTASTIC_EXCLUDE_WIFI and HAS_WIFI cleanup...
Our code was checking HAS_WIFI and the new MESHTASTIC_EXCLUDE_WIFI
flags in various places (even though EXCLUDE_WIFI forces HAS_WIFI
to 0).  Instead just check HAS_WIFI, only use EXCLUDE_WIFI inside
configuration.h

* cleanup: use HAS_NETWORKING instead of HAS_WIFI || HAS_ETHERNET
We already had HAS_NETWORKING as flag in MQTT to mean 'we have
tcpip'.  Generallize that and move it into configuration.h so that
we can use it elsewhere.

* Use #pragma once, because supported by gcc and all modern compilers
instead of #ifdef DOTHFILE_H etc...

---------

Co-authored-by: Jonathan Bennett <jbennett@incomsystems.biz>

src/RedirectablePrint.cpp

@@ -16,7 +16,7 @@
 #include "platform/portduino/PortduinoGlue.h"
 #endif
 
-#if HAS_WIFI || HAS_ETHERNET
+#if HAS_NETWORKING
 extern Syslog syslog;
 #endif
 void RedirectablePrint::rpInit()
@@ -138,7 +138,7 @@ void RedirectablePrint::log_to_serial(const char *logLevel, const char *format,
 
 void RedirectablePrint::log_to_syslog(const char *logLevel, const char *format, va_list arg)
 {
-#if (HAS_WIFI || HAS_ETHERNET) && !defined(ARCH_PORTDUINO)
+#if HAS_NETWORKING && !defined(ARCH_PORTDUINO)
     // if syslog is in use, collect the log messages and send them to syslog
     if (syslog.isEnabled()) {
         int ll = 0;