Docker: pass Options.platform to inspect and default local platform to linux/$GOARCH

[bojidar-bg]

Fixes buildpacks/lifecycle#1599 in my testing.

Possible issues:

• Changing the default platform of imgutils.local to match the current binary's architecture is a partial revert of Use daemon or runtime provided arch instead of amd64 #232. I'd rather change it to default to linux/$GOARCH always (and not just when daemonInfo.Os == "linux"), for parity with remote, but I don't know if that will break other packages depending on imgutils. 😅
• If the base image's architecture does not match the architecture of the wanted platform, the old code used to return the base image anyway. With this change, it would instead error out. Fixed!

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 34.06%. Comparing base (08327da) to head (ee231a0).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #302      +/-   ##
==========================================
+ Coverage   33.79%   34.06%   +0.28%     
==========================================
  Files          39       39              
  Lines        3283     3301      +18     
==========================================
+ Hits         1109     1124      +15     
- Misses       1980     1982       +2     
- Partials      194      195       +1     

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[jabrown85]

This looks like a good idea to me! Left a couple comments to address

[jabrown85]

We have some tests here around not having a platform defined. I was surprised there weren't any correlated test changes. Should there be a test to capture this new behavior?

[bojidar-bg]

If I'm reading #283 correctly, in the test environment, both the Docker daemon and the imgutil tests run on the same architecture, amd64, hence this ends up causing no change.

A new test would be nice, but I'm not very sure how to introduce it.

[bojidar-bg]

Comments should be handled now; unsure how to add a new test for mismatched architecture between imgutil and the Docker host.