apt_dpkg: discard cached contents mapping on OSError

[bdrung]

test_retrace_jammy_sandbox might fail in a autopkgtest VM:

Traceback (most recent call last):
  File "/usr/bin/apport-retrace", line 713, in <module>
    sys.exit(main(sys.argv[1:]))
             ~~~~^^^^^^^^^^^^^^
  File "/usr/bin/apport-retrace", line 542, in main
    sandbox, cache, outdated_msg = apport.sandboxutils.make_sandbox(
                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        report,
        ^^^^^^^
    ...<6 lines>...
        options.dynamic_origins,
        ^^^^^^^^^^^^^^^^^^^^^^^^
    )
    ^
  File "/usr/lib/python3/dist-packages/apport/sandboxutils.py", line 274, in make_sandbox
    pkgs = needed_runtime_packages(report, pkgmap_cache_dir, pkg_versions, verbose)
  File "/usr/lib/python3/dist-packages/apport/sandboxutils.py", line 103, in needed_runtime_packages
    pkg = packaging.get_file_package(
        line,
    ...<3 lines>...
        arch=report.get("Architecture"),
    )
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 800, in get_file_package
    return self._search_contents(file, map_cachedir, release, arch)
           ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 1752, in _search_contents
    contents_mapping = self._get_file2pkg_mapping(map_cachedir, release, arch)
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 1726, in _get_file2pkg_mapping
    file2pkg = self._contents_mapping(map_cachedir, release, arch)
  File "/usr/lib/python3/dist-packages/apport/packaging_impl/apt_dpkg.py", line 340, in _contents_mapping
    self._contents_mapping_obj = pickle.load(fp)
                                 ~~~~~~~~~~~^^^^
EOFError: Ran out of input

Discard the cache in those cases and just rebuild them.

Bug: https://launchpad.net/bugs/2149911

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.48%. Comparing base (713829f) to head (7179c4c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #593      +/-   ##
==========================================
+ Coverage   84.47%   84.48%   +0.01%     
==========================================
  Files         106      106              
  Lines       21053    21080      +27     
  Branches     3223     3227       +4     
==========================================
+ Hits        17784    17810      +26     
+ Misses       2793     2792       -1     
- Partials      476      478       +2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.