feat: allow adapters to override getRequest and setResponse

[ottomated]

This enables the cloudflare adapter to emulate the Request.cf property and later handle websockets responses.

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[pkg-svelte-dev]

Install the latest version of @sveltejs/kit from d5c89b8:

pnpm add https://pkg.svelte.dev/@sveltejs/kit/c/d5c89b88cff8ff429493c8aa6dc226c7dbf52141

Open in pkg.svelte.dev: https://pkg.svelte.dev/repos/kit/pr/16753

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🦋 Changeset detected

Latest commit: d5c89b8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@sveltejs/kit	Minor

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-16753-svelte.vercel.app/