BUG/MEDIUM: http-act: Make a copy of the sample expr in (set/add)-headers-bin

BUG/MEDIUM: http-act: Make a copy of the sample expr in (set/add)-headers-bin

For set-headers-bin and add-header-bin actions, the new HTX headers to add
or set are extracted from the result of a sample expression evaluation. This
result must be copied because it is based a static trash chunk and internal
functions manipulating HTX messages also use static chunks. So to not
overwrite the sample expression, for instance because a defrag is performed,
it must be copied into a dynamically allocated chunk.

It is also important because the sample expression may be based on part of
the HTX message itself.

This patch must be backported to 3.4.