Allow specification of display_name on inputs

[freakabcd]

Allow inputs on nodes to specify a display name. Currently, all inputs are forced to use the name of the python variable being used to declare the input. At a minimum these are not allowed:

• python keywords
• spaces

This change will allow node inputs to specify a display_name property during declaration. the display_name property is used on the frontend if present, If not specified, identical behaviour to current master branch is preserved. Here is an example with temporarily modified KSampler node:

[k-imran]

Please don't merge! theres an issue with running workflows. backend -> frontend is all good. Executing workflows (frontend->backend) has issues

[MaraScott]

please have a look to that https://github.com/comfyanonymous/ComfyUI/compare/master...MaraScott:ComfyUI:master