cli-plugins/manager: IsNotFound: don't depend on causer interface

[thaJeztah]

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.17%. Comparing base (ce30966) to head (7f8c43e).
Report is 21 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5794      +/-   ##
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- Coverage   59.44%   59.17%   -0.27%     
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  Files         347      353       +6     
  Lines       29394    29472      +78     
==========================================
- Hits        17472    17440      -32     
- Misses      10950    11059     +109     
- Partials      972      973       +1     

[Benehiko]

Would you be able to add more context to the commit on why this needs to change?
The error could also be wrapped multiple times before it's a notFound type. Are we sure we never wrap the error more than once?

[Benehiko]

We can also get this one merged soon if you'd like. I don't have the full context yet though (see previous comment), but the change seems alright.

[thaJeztah]

Oh! Sorry forgot about this one; I need to double-check if this could cause a change in behavior; considering that errors.As does a deep-first match, which could result in some different semantics; ran into that when looking at using the containerd errdefs package; moby/moby#49378 (comment)