fix: set current platform as default platform when retrieving image entrypoint. Fixes #15058

[guamian-delicious]

…trypoint from container registry

Fixes #15058 Default platform linux/amd64 used when retrieving image entrypoint from container registry

Motivation

to fix an issue as above

Modifications

set default platform as current node platform when retrieving image entrypoint config from registry

Verification

i build the new binary and run it in my own dev environment

Documentation

Summary
This PR fixes a platform compatibility issue where Argo Workflows would fail to retrieve image configurations for non-linux/amd64 architectures when no commandis specified in the workflow template.

Changes

1. Modified image configuration lookup to explicitly specify the node's platform architecture
2. Added platform detection using runtime.GOOS and runtime.GOARCH
3. Ensured compatibility with multi-arch images and single-arch images on matching platforms

Impact
Before this fix:
Workflows would fail with "MANIFEST_UNKNOWN" error when:

• Using single-architecture images (ARM, etc.)
• Running on non-AMD64 nodes
• No commandspecified in template

After this fix:

• Workflows automatically use the correct platform architecture for image config lookup
• Supports ARM64, AMD64, and other architectures transparently
• Maintains backward compatibility

[jswxstw]

"v12" -> "pkgv1" seems better to me.