tests: poc snapd snap spread tests

[valentindavid]

#13370 + changes in spread tests to use the new snap.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 78.83%. Comparing base (ab996a0) to head (534fff4). Report is 215 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master   #13517      +/-   ##
==========================================
- Coverage   78.86%   78.83%   -0.03%     
==========================================
  Files        1043     1046       +3     
  Lines      134595   136020    +1425     
==========================================
+ Hits       106144   107237    +1093     
- Misses      21837    22083     +246     
- Partials     6614     6700      +86     

Flag	Coverage Δ
unittests	78.83% <100.00%> (-0.03%)	:arrow_down:

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[valentindavid]

depends on core22 lastest/stable to have the symlink fix:

• tests/nested/manual/recovery-system-reboot

depends on ubuntu-image being updated with https://github.com/snapcore/snapd/pull/13817:

• tests/nested/manual/uc20-install-in-initrd
• tests/nested/manual/core20-preseed

Still need investigation:

• tests/nested/manual/snapd-removes-vulnerable-snap-confine-revs