Update Zig version to latest master build

[hulto]

The Zig version used in the devcontainer (and consequently in CI builds that use this Dockerfile) was outdated. This PR updates ZIG_VERSION in .devcontainer/Dockerfile to 0.16.0-dev.2905+5d71e3051, which is the latest master build as of today. This ensures that cargo-zigbuild and other tools relying on Zig have the most recent toolchain.

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PR created automatically by Jules for task 720058169787344440 started by @hulto

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[github-actions]

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
2813    ±0	2813    ±0	0    ±0	0    ±0	0    ±0	0    ±0	1ms    ±0

Previous Results

Build 🏗️	Result 🧪	Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
#1715	✅	2813	2813	0	0	0	0	39.9s

Insights

Average Tests per Run	Total Flaky Tests	Total Failed	Slowest Test (p95)
2813	0	0	6.2s

Slowest Tests

Test 📝	Results 📊	Duration (avg) ⏱️	Duration (p95) ⏱️
TestDockerExecutor_Build_ContextCancellation	1	6.2s	6.2s
eldritch-libsys: std::dll_inject_impl::tests::test_dll_inject_simple	1	5.2s	5.2s
TestInteractiveShell	1	5.0s	5.0s
TestOtherStreamOutput	1	5.0s	5.0s
imix::bin/imix: install::tests::test_install_execution	3	1.8s	4.9s
imix::bin/imix: install::tests::test_install_execution	3	1.8s	4.9s
imix::bin/imix: install::tests::test_install_execution	3	1.8s	4.9s
TestDockerExecutor_Build_SimpleEcho	1	4.0s	4.0s
imix::bin/imix: tests::task_tests::test_task_eprint_behavior	3	3.0s	3.0s
imix::bin/imix: tests::task_tests::test_task_streaming_output	3	3.0s	3.0s

_{🎉 No failed tests in this run. | 🍂 No flaky tests in this run.}

Github Test Reporter by CTRF 💚