apt_dpkg: use collections.OrderedDict for packages

[bdrung]

make_sandbox is the only user. duplicates are not possible there.

[codecov]

Codecov Report

Attention: Patch coverage is 13.63636% with 19 lines in your changes missing coverage. Please review.

Project coverage is 71.44%. Comparing base (d38a3ed) to head (d0d4a75).

Files with missing lines	Patch %	Lines
apport/packaging_impl/apt_dpkg.py	13.63%	19 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (d38a3ed) and HEAD (d0d4a75). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (d38a3ed)	HEAD (d0d4a75)
	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #455       +/-   ##
===========================================
- Coverage   83.61%   71.44%   -12.17%     
===========================================
  Files         101      101               
  Lines       20464    20468        +4     
  Branches     3219     3219               
===========================================
- Hits        17111    14624     -2487     
- Misses       2858     5406     +2548     
+ Partials      495      438       -57     

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