Improve handling of remote sync saving

* Fixes sporadic failures on gui tests on Windows
* Corrects inability to write to temporary config file while running tests
* Corrects errors when using MockRemoteProcess due to missing functions

tests/mock/MockRemoteProcess.cpp

@@ -32,6 +32,7 @@ void MockRemoteProcess::start(const QString&)
 
 qint64 MockRemoteProcess::write(const QString& data)
 {
+    m_data.append(data.toUtf8());
     return data.length();
 }
 
@@ -54,3 +55,13 @@ int MockRemoteProcess::exitCode() const
 {
     return 0; // always return success
 }
+
+QString MockRemoteProcess::readOutput()
+{
+    return {};
+}
+
+QString MockRemoteProcess::readError()
+{
+    return {};
+}

tests/mock/MockRemoteProcess.h

@@ -32,6 +32,8 @@ public:
     void closeWriteChannel() override;
     bool waitForFinished(int msecs) override;
     [[nodiscard]] int exitCode() const override;
+    virtual QString readOutput() override;
+    virtual QString readError() override;
 
 private:
     QByteArray m_data;