Given a partial map files from source unit names to file contents, a list of
remappings and a list of ImportResolvers - resolvers, find all
files that are imported from the starting set files but are
missing in files and add them into the files map. Also for each imported file
add a mapping from its source unit name to the actual file name in fileNames.
Given a partial map
filesfrom source unit names to file contents, a list ofremappingsand a list ofImportResolvers -resolvers, find all files that are imported from the starting setfilesbut are missing infilesand add them into thefilesmap. Also for each imported file add a mapping from its source unit name to the actual file name infileNames.