Netty being pushed based and lolhttp pull based, a lot of complexity
was hidden in the Netty integration. Migration were painful as this
code was super sensible to race conditions.

This commit replace the underlying network & http codec implementation
by http4s blaze. At the same time we upgrade cats, cats-effect & fs2
dependencies.

- HTTP/2 support is not promoted anymore for now. It is somehow supported
by blaze but it requires ALPN support that is not widely supported in Java
for now. We will introduce it back later.

- Protocol upgrade in user-land API has been removed. It was never used
and I'm not sure anymore that it is useful as new protocol seems to
favor ALPN anyway.

- Auto follow-redirect is not supported anymore when re-using  a client
directly connected to an host. It does not make sense as redirect to
another host is perfectly legit but it can't be handled if the client is
connected to a singel host. It was a bug in the initial design.