[v11] Gate incoming HTTP body capture on `dataCollection.httpBodies`

[chargome]

Incoming request bodies are captured at maxRequestBodySize: 'medium' unconditionally across all server SDKs. The spec defines httpBodies defaulting to [](off) — captured only when 'incomingRequest' is listed. Flipping this now would silently drop bodies for existing users, so it's deferred to v11.

Default is 'medium' and ignores dataCollection.httpBodies in:

- core
- node-core
- node
- deno
- cloudflare

bun + framework SDKs inherit transitively.

In v11, derive maxRequestBodySize from httpBodies.includes('incomingRequest') (explicit maxRequestBodySize still overrides).

[linear-code]

JS-2649