Get rid of QtcProcess::workingDirectory() overload

Adapt all callers' code so that it passes the FilePath
instead of QString. As a consequence introduce
TemporaryDirectory::masterDirectoryFilePath() and use
it where easily possible.

Change-Id: I14564949b3b916921e32a2957c84c03d1da43af2
Reviewed-by: hjk <hjk@qt.io>

src/libs/utils/qtcprocess.cpp

@@ -678,11 +678,6 @@ void QtcProcess::setWorkingDirectory(const FilePath &dir)
     d->m_workingDirectory = dir;
 }
 
-void QtcProcess::setWorkingDirectory(const QString &dir)
-{
-    setWorkingDirectory(FilePath::fromString(dir));
-}
-
 void QtcProcess::setUseCtrlCStub(bool enabled)
 {
     // Do not use the stub in debug mode. Activating the stub will shut down