feat: implement creating `ManifestList` from single platform images

[renzodavid9]

Fixes: #7632 Related: #7082

Description

In this PR, Skaffold will iteratively create single platform images for builders that don't support native multi-arch builds, and then generate a ManifestList programmatically that consists of these individual platform manifests.

User facing changes Users can now provide multiple arguments to the --platform flag.

Testing instructions:

1. In the examples/getting-started project, run:

   skaffold build --default-repo=your/container/registry --platform=linux/amd64,linux/arm64
   

2. You should get the output:

   ...
   Building [skaffold-example]...
   Target platforms: [linux/amd64,linux/arm64]
   ...
   [+] Building 0.3s (13/13) FINISHED
   ...
   => => writing image sha256:10af3142e460566f5791c48758f0040cef6932cbcb0766082dcbb0d8db7653e7
   => => naming to gcr.io/k8s-skaffold/skaffold-example:latest_linux_amd64
   ...
   latest_linux_amd64: digest: sha256:15bd4f2380e99b3563f8add1aba9691e414d4cc5701363d9c74960a20fb276c4 size: 739
   ...
   [+] Building 52.8s (13/13) FINISHED
   ...
   => => writing image sha256:68866691e2d6f079b116e097ae4e67a53eaf89e825b52d6f31f2e9cc566974de
   => => naming to gcr.io/k8s-skaffold/skaffold-example:latest_linux_arm64
   ...
   4e0c2525c370: Pushed
   latest_linux_arm64: digest: sha256:868d0aec1cc7d2ed1fa1e840f38ff1aa50c3cc3d3232ea17a065618eaec4e82b size: 739
   Build [skaffold-example] succeeded
   

3. Run the following docker command to validate the built image:

   docker manifest inspect your/container/registry/skaffold-example:latest | grep -A 3 "platform"
   
     "platform": {
         "architecture": "amd64",
         "os": "linux"
     }
   --
     "platform": {
         "architecture": "arm64",
         "os": "linux"
     }
   

Pending

• [ ] Add unit tests for the CreateManifestList function.
• [ ] Add integration test using examples/getting-started.

[codecov[bot]]

Codecov Report

Merging #7745 (28107eb) into main (290280e) will decrease coverage by 3.95%. The diff coverage is 53.59%.

@@            Coverage Diff             @@
##             main    #7745      +/-   ##
==========================================
- Coverage   70.48%   66.52%   -3.96%     
==========================================
  Files         515      589      +74     
  Lines       23150    28316    +5166     
==========================================
+ Hits        16317    18837    +2520     
- Misses       5776     8107    +2331     
- Partials     1057     1372     +315     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/credits/export.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/deploy.go	40.90% <0.00%> (-12.94%)	:arrow_down:
cmd/skaffold/app/cmd/test.go	44.44% <0.00%> (ø)
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	:arrow_down:
cmd/skaffold/app/cmd/render.go	35.48% <18.18%> (-5.90%)	:arrow_down:
cmd/skaffold/app/cmd/lsp.go	28.12% <28.12%> (ø)
cmd/skaffold/app/cmd/run.go	64.28% <33.33%> (-9.63%)	:arrow_down:
cmd/skaffold/app/cmd/fix.go	56.41% <37.50%> (-20.07%)	:arrow_down:
cmd/skaffold/app/cmd/verify.go	41.17% <41.17%> (ø)
... and 349 more

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[gsquared94]

discussed offline; we'll complete the pending tasks in a follow up PR. Merging this for integration testing with other PRs.