Support --unhandled-rejections flag and rejectionHandled event

[pfgithub]

TODO:

• 'strict'
• 'warn'
  • fails to warn for -p 'Promise.reject("abc")', the nextTick never executes
• 'warn-with-error-code'
• why does hot.test.ts should work with sourcemap generation fail when the command has --unhandled-rejections=bun? the error's location is marked on Error() instead of on new

[robobun]

^{Updated 3:07 PM PT - May 27th, 2025}

❌ @pfgithub, your commit ff96b0d has 5 failures in Build #17430:

• test/js/third_party/@duckdb/node-api/duckdb.test.ts - segmentation fault on 🐧 20.04 x64-baseline
• test/bake/dev/stress.test.ts - 1 failing on 🐧 12 x64-baseline
• test/js/node/test/parallel/test-http2-session-unref.js - timeout on 🐧 24.04 aarch64
• test/js/node/test/parallel/test-http2-session-unref.js - timeout on 🐧 20.04 aarch64
• test/js/node/test/parallel/test-http2-session-unref.js - timeout on 🐧 24.04 x64
• test/js/node/test/parallel/test-http2-session-unref.js - timeout on 🐧 20.04 x64
• test/js/node/test/parallel/test-http2-session-unref.js - timeout on 🐧 24.04 x64-baseline
• test/js/node/test/parallel/test-http2-session-unref.js - timeout on 🐧 20.04 x64-baseline
• test/js/node/test/parallel/test-ttywrap-stack.js - code 1 on 🍎 13 aarch64
• test/js/node/test/parallel/test-ttywrap-stack.js - code 1 on 🍎 14 aarch64
• test/js/node/test/parallel/test-ttywrap-stack.js - code 1 on 🐧 12 aarch64
• test/js/node/test/parallel/test-ttywrap-stack.js - code 1 on 🐧 24.04 aarch64
• test/js/node/test/parallel/test-ttywrap-stack.js - code 1 on 🐧 20.04 aarch64
• test/js/node/test/parallel/test-ttywrap-stack.js - code 1 on 🐧 3.21 x64
• test/js/bun/spawn/spawn.test.ts - 1 failing on 🪟 2019 x64-baseline
• test/js/bun/spawn/spawn.test.ts - 1 failing on 🪟 2019 x64

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🧪   To try this PR locally:

bunx bun-pr 19874

That installs a local version of the PR into your bun-19874 executable, so you can run:

bun-19874 --bun