REGTESTS: http-rules: test the binary header manipulation actions

REGTESTS: http-rules: test the binary header manipulation actions

The add-headers-bin, set-headers-bin and del-headers-bin actions had no
coverage at all. The test saves the incoming header block with
req.hdrs_bin, drops a few headers and restores them from the saved
block, with and without the "prefix" filter, and checks on the server
side which headers made it through.

The lists passed to del-headers-bin are built by hand with the bin()
fetch so that the varint encoding of the header names is exercised too,
with the default exact matching and with the "beg" one.