Have ConfigManager cleanup its temporary directory on destruction (LP #1959729)

[Caligatio]

Description

ConfigManager creates a temporary directory on instantiation and relies on the caller to clean up that temporary directory despite never exposed directly to the caller. Due to the code structure in several places, it would be onerous to call ConfigManager.cleanup() everywhere it's needed so this patch instead calls .cleanup() whenever the ConfigManager instance is garage collected.

This addresses https://bugs.launchpad.net/netplan/+bug/1959729

Checklist

• Runs make check successfully.
• Retains 100% code coverage (make check-coverage).
• New/changed keys in YAML format are documented.
• (Optional) Adds example YAML for new feature.
• (Optional) Closes an open bug in Launchpad.

[codecov-commenter]

Codecov Report

Merging #259 (de4af02) into main (49e5583) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #259   +/-   ##
=======================================
  Coverage   99.14%   99.14%           
=======================================
  Files          60       60           
  Lines       10494    10511   +17     
=======================================
+ Hits        10404    10421   +17     
  Misses         90       90           

Impacted Files	Coverage Δ
netplan/configmanager.py	100.00% <100.00%> (ø)
tests/test_configmanager.py	100.00% <100.00%> (ø)

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[slyon]

Thank you Brian, this issue has been bugging me for a long time!
Your code provides a clean and self-contained solution to this problem and I like this approach.

configmanager.py is currently being reworked heavily (in #255) but the tmpdir cleanup on destruction is a good thing to have independently. All tests and coverage are passing (I ran the integration tests locally, see below). This is ready for merging.

autopkgtest [10:44:40]: @@@@@@@@@@@@@@@@@@@@ summary
ovs                  PASS
ethernets            PASS
bridges              PASS
bonds                PASS
routing              PASS
vlans                PASS
wifi                 PASS
tunnels              PASS
scenarios            PASS
regressions          PASS
autostart            PASS
cloud-init           PASS

[schopin-pro]

Late to the party, but thanks for looking into this. I'd noticed a whole bunch of netplan dirs in /tmp a while back but I assumed it was operator error (I'd usually force-kill the test suite a bunch of time when investigating stuff with gdb).