Support profiling the startup phase of a Worker

.changeset/rich-pots-mate.md

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+"wrangler": minor
+---
+
+Add `--outfile` to `wrangler deploy` for generating a worker bundle.
+
+This is an advanced feature that most users won't need to use. When set, Wrangler will output your built Worker bundle in a Cloudflare specific format that captures all information needed to deploy a Worker using the [Worker Upload API](https://developers.cloudflare.com/api/resources/workers/subresources/scripts/methods/update/)

.changeset/startup-profiling.md

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+---
+"wrangler": minor
+---
+
+Add a `wrangler check startup` command to generate a CPU profile of your Worker's startup phase.
+
+This can be imported into Chrome DevTools or opened directly in VSCode to view a flamegraph of your Worker's startup phase. Additionally, when a Worker deployment fails with a startup time error Wrangler will automatically generate a CPU profile for easy investigation.
+
+Advanced usage:
+
+- `--deploy-args`: to customise the way `wrangler check startup` builds your Worker for analysis, provide the exact arguments you use when deploying your Worker with `wrangler deploy`. For instance, if you deploy your Worker with `wrangler deploy --no-bundle`, you should use `wrangler check startup --deploy-args="--no-bundle"` to profile the startup phase.
+- `--worker-bundle`: if you don't use Wrangler to deploy your Worker, you can use this argument to provide a Worker bundle to analyse. This should be a file path to a serialised multipart upload, with the exact same format as the API expects: https://developers.cloudflare.com/api/resources/workers/subresources/scripts/methods/update/