Limit number of bytes read from HTTP request bodies

[rhcarvalho]

See SDK development docs:

[request].data:
Optional. Submitted data in a format that makes the most sense. SDKs should discard large bodies by default. Can be given as string or structural data of any format.

See sentry-dotnet implementation as a reference.

We can use an io.LimitedReader and an io.MultiReader to limit the number of bytes the Sentry SDK reads, while still allowing the downstream handlers to read the full body.

The limits should be applied at least in Request.FromHTTPRequest.