BUG/MEDIUM: mux-h1; Ignore headers modifications about payload representation

BUG/MEDIUM: mux-h1; Ignore headers modifications about payload representation

We now ignore modifications during the message analysis about the payload
representation if only headers are updated and not meta-data. It means a C-L
header removed to add a T-E one or the opposite via HTTP actions. This kind
of changes are ignored because it is extremly hard to be sure the payload
will be properly formatted.

It is an issue since the HTX was introduced and it was never reported. Thus,
there is no reason to backport this patch for now. It relies on following commits:

  * MINOR: mux-h1: Add flags if outgoing msg contains a header about its payload
  * MINOR: mux-h1: Rely on H1S_F_HAVE_CHNK to add T-E in outgoing messages
  * BUG/MEDIUM: mux-h1: Add C-L header in outgoing message if it was removed