Introduce bun.dns.prefetch API

[Jarred-Sumner]

What does this PR do?

This adds the bun.dns.prefetch API.

import {dns} from "bun";

dns.prefetch("bun.sh", 443);
//
// ... sometime later ...
await fetch("https://bun.sh");

Like <link rel="dns-prefetch"> in browsers, the intended usecase is to amortize the cost of DNS lookups you know you'll make soon.

This also sets the DNS cache to have a TTL of 30 seconds. For reference, the Java Virtual Machine has no TTL set and AWS recommends 5 seconds.

This also introduces a dns.getCacheStats() API which exposes information about the DNS cache.

This also adds documentation.

This also makes bun install prefetch the DNS query.

How did you verify your code works?

There is a test

[github-actions]

❌ @Jarred-Sumner, your commit has failing tests :(

💪 1 failing tests Darwin AARCH64

• test/js/bun/http/serve.test.ts 1 failing

💻 1 failing tests Darwin x64 baseline

• test/js/bun/http/serve.test.ts 2 failing

💻 2 failing tests Darwin x64

• test/cli/install/bun-create.test.ts 1 failing
• test/js/bun/http/serve.test.ts 1 failing

🐧🖥 2 failing tests Linux x64 baseline

• test/integration/mysql2/mysql2.test.ts 3 failing
• test/js/node/child_process/child_process-node.test.js 1 failing

🐧🖥 1 failing tests Linux x64

• test/cli/install/bun-install.test.ts 2 failing

🪟💻 8 failing tests Windows x64 baseline

• test/bundler/large_asset_regression.test.ts 1 failing
• test/cli/install/bunx.test.ts 1 failing
• test/integration/esbuild/esbuild.test.ts 1 failing
• test/js/bun/shell/bunshell.test.ts 1 failing
• test/js/node/dns/node-dns.test.js 2 failing
• test/js/node/process/process.test.js 2 failing
• test/js/node/watch/fs.watchFile.test.ts SIGTERM
• test/js/web/workers/worker.test.ts 2 failing

🪟💻 9 failing tests Windows x64

• test/cli/install/bunx.test.ts 1 failing
• test/cli/install/registry/bun-install-registry.test.ts 1 failing
• test/integration/esbuild/esbuild.test.ts 1 failing
• test/integration/next-pages/test/dev-server.test.ts 1 failing
• test/js/bun/shell/bunshell.test.ts 1 failing
• test/js/node/dns/node-dns.test.js 2 failing
• test/js/node/process/process.test.js 2 failing
• test/js/node/watch/fs.watchFile.test.ts SIGTERM
• test/js/web/workers/worker.test.ts 2 failing

View logs

[mangs]

would be useful to see these values per hostname as well to see where lookup activity is concentrated. could generate some useful graphs from this too.