feat(http-request-body): allow users to specify a request body in the HTTP module

[lc]

This PR allows users to specify a HTTP request body in the http module via a new flag called -request-body

How to Test

zgrab2 http -p 80 --method POST --request-body='{"test":"true"}' --custom-headers-names='Content-Type' --c
ustom-headers-values='application/json'

Notes & Caveats

I needed to be able to POST a request body to fingerprint a specific webservice.

I found this older PR was open, but when I tried using this fork, it didn't work

So I wrote this quickly.

[mzpqnxow]

@lc thank you for picking this up! I felt bad I never got around to re-basing it