HttpEventHandler.body should avoid being resized

Handling chunks requires appending Buffer(s) in the body stored at HttpEventHandler.
See
https://github.com/eclipse-vertx/vert.x/blob/d5f613c69cf6ed3a9ed3586e5be1896b11711462/vertx-core/src/main/java/io/vertx/core/http/impl/HttpEventHandler.java#L54

This can both create excessive heap footprint and performing useless copies.
It would be ideal if we could retain the chunks accumulating them in some list or queue and eventually allocating a single buffer to copy or transferring them to a composite buffer (without copying anything).
I have used a similar strategy in https://github.com/quarkusio/quarkus/blob/b870c90569a4c88467313587565205818034f4df/independent-projects/vertx-utils/src/main/java/io/quarkus/vertx/utils/AppendBuffer.java#L19