• extracted from Another hr button fix  #14728

change identifying a script from using Scripts class name to Scripts internal name an as not all Script have unique names

raise RuntimeError when there's issue

reason the identifying a script using class name is problematic as currently as there's no convention to using unique names with there Script class name
in base webui alone we have multiple scripts that are all called Scripts
not to mention lots of extensions use the same Script name for the Script

hence the change to using the scrip internal name

using == to match elem_id

• and as opposed to returning none when there is an issue like script or element id is not found, raise runtime error

• even though comparing the element ID using in is convenient as it allows you to ignore stuff like the prefix txt2img_ in txt2img_seed but this would cause a potential issue in that depending on the order of your arg
  for example if you have two elements args with IDs of seed and subseed
  if the order of the args is ['seed', 'subseed'] then everything function as normal
  but if the order is ['subseed', 'seed'] when matching for seed it be match with subseed
  hence changed to using ==

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• I have read contributing wiki page
• I have performed a self-review of my own code
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