fix(unikontainers): preserve slice order when removing element

[mdryaan]

Description

remove() in pkg/unikontainers/utils.go removed an element by swapping it with the last element before truncating. This destroyed the ordering of all remaining elements. Both call sites are affected: handleQueueProxy (removes SERVING_READINESS_PROBE from spec.Process.Env) and the vAccel env cleanup in unikontainers.go (removes VACCEL_RPC_ADDRESS). Replace the swap-and-truncate with append(s[:i], s[i+1:]...) to preserve order.

Related issues

• Fixes Preserve slice order when removing environment variable #677

How was this tested?

Added TestRemovePreservesOrder to pkg/unikontainers/utils_test.go. The test
calls remove([]string{"a", "b", "c", "d"}, 0) and asserts the result is
["b", "c", "d"].

Before fix:

After fix:

Run with:
go test ./pkg/unikontainers/ -v -run TestRemovePreservesOrder

golangci-lint run passes with 0 issues. make builds successfully.

LLM usage

N/A

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr, make test_nerdctl, make test_docker, make test_crictl).
• If LLMs were used: I have read the llm policy.

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[mdryaan]

Hey @cmainas , Could you please have a look at this PR whenever you have time? Thanks!