Procrunner

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* Drop Python 3.6 support
* The run() function now returns a subprocess.CompletedProcess object,
which no longer allows array access operations
(those were deprecated in `60 <https://github.com/DiamondLightSource/python-procrunner/pull/60>`_)
* The run() argument 'raise_timeout_exception' is now set by default,
a 'False' value will lead to a UserWarning and a behavioural change.
The argument is now deprecated and will be removed in a future version.
(previously introduced in `61 <https://github.com/DiamondLightSource/python-procrunner/pull/61>`_)
* Calling the run() function with multiple unnamed arguments is no longer supported
(previously deprecated in `62 <https://github.com/DiamondLightSource/python-procrunner/pull/62>`_)
* The run() function no longer accepts a 'debug' argument
(previously deprecated in `63 <https://github.com/DiamondLightSource/python-procrunner/pull/63>`_)

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* Allow specifying 'preexec_fn' and 'creationflags' keywords, which will be passed through to
the subprocess call

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* The run() function now understands stdin=subprocess.DEVNULL to close the subprocess stdin,
rather than to connect through the existing stdin, which is the current default

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* Add Python 3.10 support

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* Add Python 3.9 support, drop Python 3.5 support
* Fix a file descriptor leak on subprocess execution

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* Calling the run() function with unnamed arguments (other than the command
list as the first argument) is now deprecated. As a number of arguments
will be removed in a future version the use of unnamed arguments will
cause future confusion. `Use explicit keyword arguments instead (62). <https://github.com/DiamondLightSource/python-procrunner/pull/62>`_
* `The run() function debug argument has been deprecated (63). <https://github.com/DiamondLightSource/python-procrunner/pull/63>`_
This is only used to debug the NonBlockingStream* classes. Those are due
to be replaced in a future release, so the argument will no longer serve
a purpose. Debugging information remains available via standard logging
mechanisms.
* Final version supporting Python 3.5