group related single-cell parameters into opt.singlecell list argument

write bambu.singlecell() & bambu.spatial() function wrapper to run bambu in single-cell mode:

• use the basic parameters (data, transcript discovery, transcript quantification) with opt.singlecell argument
• wrap the code in Custom single-cell and spatial section in the main documentation in devel_pre_v4 under bambu.singlecell() call (we expect users only have to run one bambu.singlecell() to get the output instead of running multiple lines of code)

update arguments related to the issue:

• demultiplexed (automatically set to TRUE in bambu.singlecell())
  • remove the option to provide reads-to-barcode mappng .csv file
  • rename with extractBarcodeUMI
• clusters (include in opt.singlecell)
  • fix bug when provided as a barcode-to-cluster csv file (do we need that actually?)
• dedupUMI (include in opt.singlecell)
  • nothing to change, to be included as an element in opt.singlecell list for bambu.singlecell() call
• barcodesToFilter, sampleName, cleanReads
  • remove the parameters