fix: conditionally access builder properties that only exist on the latest SvelteKit

[teemingc]

fixes #14232

We overlooked that some people might update their adapters but not SvelteKit, so those new instrumentation builder methods wouldn't exist and they get null pointer errors. Simon usually catches these but I always forget.

This PR fixes that and future-proofs it by making new builder properties possibly undefined so that we get type errors and can catch these earlier.

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🦋 Changeset detected

Latest commit: 0aa696c

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

This PR includes changesets to release 4 packages

Name	Type
@sveltejs/adapter-cloudflare	Patch
@sveltejs/adapter-netlify	Patch
@sveltejs/adapter-vercel	Patch
@sveltejs/adapter-node	Patch

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[dummdidumm]

Great solution that relieves me from thinking about/catching this 😁👍

[dummdidumm]

Mhm still some type errors but once you fixed them you can hit merge (am AFK right now)

[teemingc]

Mhm still some type errors but once you fixed them you can hit merge (am AFK right now)

Should be fixed now.