[posix] add Thread network default interface name configuration

The default Thread interface name `wpan0` has been occupied by
other programs in Android. Thread network has to use other
network interface name. Then users have to specify an interface
name when they are using the command `ot-ctl`. It's very inconvenient.

This commit adds a configuration for developers to set their
default Thread interface name.

src/posix/client.cpp

@@ -238,7 +238,7 @@ static bool ShouldEscape(char aChar)
 
 Config ParseArg(int &aArgCount, char **&aArgVector)
 {
-    Config config = {"wpan0"};
+    Config config = {OPENTHREAD_POSIX_CONFIG_THREAD_DEFAULT_NET_IF_NAME};
 
     optind = 1;
 

src/posix/main.c

@@ -197,6 +197,7 @@ static void ParseArg(int aArgCount, char *aArgVector[], PosixConfig *aConfig)
     aConfig->mPlatformConfig.mPersistentInterface = false;
     aConfig->mPlatformConfig.mSpeedUpFactor       = 1;
     aConfig->mLogLevel                            = OT_LOG_LEVEL_CRIT;
+    aConfig->mPlatformConfig.mInterfaceName       = OPENTHREAD_POSIX_CONFIG_THREAD_DEFAULT_NET_IF_NAME;
 #ifdef __linux__
     aConfig->mPlatformConfig.mRealTimeSignal = SIGRTMIN;
 #endif

src/posix/platform/daemon.cpp

@@ -60,9 +60,10 @@ typedef char(Filename)[sizeof(sockaddr_un::sun_path)];
 
 void GetFilename(Filename &aFilename, const char *aPattern)
 {
-    int rval;
+    int         rval;
+    const char *netIfName = strlen(gNetifName) > 0 ? gNetifName : OPENTHREAD_POSIX_CONFIG_THREAD_DEFAULT_NET_IF_NAME;
 
-    rval = snprintf(aFilename, sizeof(aFilename), aPattern, gNetifName);
+    rval = snprintf(aFilename, sizeof(aFilename), aPattern, netIfName);
     if (rval < 0 && static_cast<size_t>(rval) >= sizeof(aFilename))
     {
         DieNow(OT_EXIT_INVALID_ARGUMENTS);

src/posix/platform/openthread-posix-config.h

@@ -252,6 +252,16 @@
 #endif
 #endif
 
+/**
+ * @def OPENTHREAD_POSIX_CONFIG_THREAD_DEFAULT_NET_IF_NAME
+ *
+ * Define the Thread defaut network interface name.
+ *
+ */
+#ifndef OPENTHREAD_POSIX_CONFIG_THREAD_DEFAULT_NET_IF_NAME
+#define OPENTHREAD_POSIX_CONFIG_THREAD_DEFAULT_NET_IF_NAME "wpan0"
+#endif
+
 #ifdef __APPLE__
 
 /**