gcode_macro: Add 'repr' and 'shell_quote' jinja2 filters and 'do' extension

[jamespharaoh]

Passing a variable through both these filters makes it easy to store any type of value, including
dictionaries and lists, using commands such as SET_GCODE_VARIABLE and SAVE_VARIABLE. The first filter repr simply calls the python function of the same name, and the second calls
pipes.quote.

Enabling the jinja2.ext.do extension makes it easier to work with these values, for example you
can set a dictionary member with {% do d.update ({k: v}) %}.

Here's an example to manage a saved dictionary of string values:

[gcode_macro DATA_SET]
gcode:
  {% set data = printer.save_variables.variables.data | default ({}) %}
  {% do data.update ({ params.NAME: params.VALUE }) %}
  SAVE_VARIABLE VARIABLE=data VALUE={data | repr | shell_quote}

In my case, I am trying to set up print profiles for different printer configurations, filament types, and print styles. Without this type of support I might use separate named variables, eg PROFILE_{profile_name}_{key}, which doesn't seem ideal. Alternatively I might try and do all the escaping myself which would likely be very messy and either incomplete (ie incorrect in edge cases) or overly complicated.

The shell_quote filter should also be useful for calling other extended gcode commands safely with runtime-generated parameter values.

[Sineos]

See #5149

[KevinOConnor]

Thanks. However, I have similar feedback to my feedback in PR #5149 (briefly, I fear this adds complexity and the result is more variants of "ugly").

Separately, I believe it should be possible to accomplish repr functionality already by using some_string.__repr__().

-Kevin

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