Clean up the main module creation loop

This change reorganizes the code within the main module creation loop
in preparation for delegating the work to separate types. It has been
split out into its own change to make it easier to review by keeping
the functional changes localized.

Renames the osTypeSpecificInfo archTypes field to archInfos as the
latter is more accurate.

Cleans up the arch variants handling:
1) Groups them by arch type to make them easier to process.
2) Fails fast when there is not exactly one variant per arch type as
   otherwise it results in a confusing failure later on.
3) Removes the commonArch flags and instead uses the fact that
   osInfo.archInfos is empty when the common architecture variant is
   available.

Cleans up the arch type specific property set handling.
1) Adds new archPropertySet variable to allow the choice of where the
   arch specific properties are added to be made alongside the choice
   of where the os specific properties are to be added.
2) Removes unnecessary check for commonArch around the loop to add
   properties from archInfos as the archInfos will be empty when the
   common architecture is present.

A number of other changes to make it easier to extract the code into
their own methods.

Test: m nothing
Bug: 142918168
Change-Id: I16a5fa79efff0d08c22916449eb46a5bd910723a