[Loadpage UI] Use PeakArea vs NormalizedPeakArea for chemoproteomics data for Spectronaut

[tonywu1999]

Story

MSstatsShiny gives no option to use either PeakArea (MS2) vs NormalizedPeakArea (MS2) vs FGMS1Quantity (MS1) for the intensity value. Users have preferences between the two, so we should enable that option.

Subtasks

• Create a dropdown allowing users to pick between PeakArea vs NormalizedPeakArea vs FGMS1Quantity.
• Pass the user option into the loadpage server as the intensity parameter of the Spectronaut converter.