Fix META/care_map.pb generation.

In https://r.android.com/1991151 we removed an extra call to
AddCareMapForAbOta() from generate_care_map(), since
AddCareMapForAbOta() is already called by add_img_to_target_files.

However, when add_img_to_target_files generated care_map.pb it
didn't have the proper partition *_image_size values set for
images copied directly from the input target files packages.
This was because the generate_care_map() function, which sets
those *_image_size values, was executed after add_img_to_target_files.

At best this meant that care_map.pb was missing some information.
At worst, care_map.pb is missing entirely (when all images are
copied instead of regenerated).

This change:
- Renames generate_care_map() to set_copied_image_size_props()
  and simplifies the logic a bit.
- Calls set_copied_image_size_props() before calling
  add_img_to_target_files. Now, add_img_to_target_files will
  have all necessary *_image_size values to perform the
  META/care_map.pb generation step.

Bug: 187432243
Bug: 221858722
Bug: 223198503
Test: Use to create a merged build that does not regenerate any images.
      Observe that META/care_map.pb is now generated as expected.
Change-Id: I1b3c8636be8cbe203222e60b1272a5e11f68589b