changing figure names to be the user-defined names to support "supplemental" type figures

[ivichadriana]

The following PR has the changes to use the user's name instead of the previously defined "Figure X" names.

• The prompts for (most) agents now include (the same) instruction to cite supplemental figures too. Currently it might now. be needed, since the name the user gives is used and there is no true difference in how main figures and supplemental figures are handled.. but it's there just in case this changes in the future.
• The most important change is using the user-given name of the figures throughout the text essentially.
• Considerations for future work: the names would ideally be "flexible" i.e., the text box should be able to be changed, and that should change the order and name that the figures are used in the text. This PR currently only includes using the first given name, not a flexible way.