Add option to preserve content decoder

[oneonestar]

Add option to preserve content decoder.

Airlift Http Client by default disable compression by removing content decoder factories.
In Trino Gateway, we are forwarding request from client to Trino using Airlift Http Client.
We would like to preserve the encoding and allow the communication between Client, Gateway and Trino to use compression.

Relates to: trinodb/trino-gateway#765

Airlift contribution check list

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[wendigo]

I've filled jetty/jetty.project#13650 so we can make it a proper implementation

[oneonestar]

https://jetty.org/docs/jetty/12.1/programming-guide/client/http.html#content-response

HttpClient httpClient = new HttpClient();
httpClient.start();
// Remove all the default response content decoders.
httpClient.getContentDecoderFactories().clear();

Looks like the .clear() is the official way to do it. I rebased the PR, PTAL.