content: don't error out on incomplete hex

content: don't error out on incomplete hex

Before 6.0.6 if hex content was incomplete, Suricata didn't error out.
With 6.0.6 incomplete hex was detected and errored on which is a
breaking change in a release branch.  Instead, only emit a warning
unless strict content checking has been requested.

To enable strict behaviour on incomplete content hex in a rule,
"--strict-rule-keywords=content" can be used on the command line.

Issue: #5546