spec. compliance regarding transfer-encoding headers

[uNetworkingAB]

There is non-standard interpretation of, for instance, two "transfer-encoding" headers. This should be added in h1spec test, and fixed.

[uNetworkingAB]

Something like this could be merged https://github.com/oven-sh/bun/pull/21737/files#diff-2b9c6c01fe853ae647d63b75e72ebbb27edac652ab9c4210e9d369f1e03e9979