fix: split ctr_test into foreground and detached contexts

[mdryaan]

Description

tests/e2e/ctr_test.go routed all test cases through a single DescribeTable calling runForegroundTest, regardless of whether a test case had a TestFunc set. Any case with a non-nil TestFunc would have it silently ignored — runForegroundTest only checks ExpectOut.

This change mirrors the pattern in nerdctl_test.go: a Context("foreground containers") block using selectTestCases(ctrTestCases(), false) calls runForegroundTest, and a Context("detached containers") block using selectTestCases(ctrTestCases(), true) calls runDetachedTest. No test case logic changes — purely structural.

Related issues

• Fixes ctr_test.go routes all test cases through runForegroundTest, silently ignoring TestFunc #68

How was this tested?

tests/e2e/ctr_test.go is the only file changed. The single DescribeTable (line 46) was replaced with two Context blocks matching nerdctl_test.go exactly. The linter passes locally (golangci-lint run -v --timeout=5m); the only reported issues are
pre-existing CRLF noise on unmodified files that Linux CI does not flag. make unittest and make pass without errors.

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.