Support for working with remote files

This epic collects all the activities related to Qt Creator remote file support.

Current situation

We have already classes Utils::FilePath and Utils::QtcProcess as convenience layers on top of QString based file names and QProcess respectively.

We are currently extending these to become the core of the needed abstraction layer for containerized builds.

Utils::FilePath is has been changed to be a structure of three strings, 'scheme', 'host' and 'path', somewhat aligned to the url-terminology. QUrl can unfortunately not be used as we need to pass host and path information that are not valid RFC 8089.

Utils::QtcProcess already supports starting remote processes transparently. Together with new ProjectExplorer::FileTransfer, also supporting remote files transparently, both classes eliminated 18 old classes that were doing it in non-transparent way (by explicit usage).