Crl.interactivesessions

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- Use Alpine Linux in docker-robottests instead of Debian

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- Fix BashShell banner reading error in slow shells by adding banner_timeout
keyword argument

- Fix hanging of the start in case in case BashShell value of tty_echo is True
while in reality the terminal echo is off

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- Add stability tests documentation back

- Improve logging by moving and requiring all logging to be under
'crl.interactivesessions' logger.

- Make _RemoteProxy and _RecursiveProxy default timeouts configurable

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- Raise FatalPythonError in MsgPythonShell.exec_command in case the remote
server has failed

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- Fix python 2 & 3 compatibility for SelfRepairingSession

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- Acknowledge server ID reply in start of MsgPythonShell