meta the arguments a bit for GET vs other request types

[jmartin-tech]

Fix #557

Tested example:

REST_API_KEY="fake" ./garak_debug.py -m rest --generator_option_file garak/resources/rest/restdemo.json -p encoding.InjectBase16

Changing restdemo.json method types using garak/resources/rest/restserv.py as server side:
post:

127.0.0.1 - - [29/Apr/2024 15:53:55] "POST /endpoint HTTP/1.1" 200 -
values CombinedMultiDict([ImmutableMultiDict([]), ImmutableMultiDict([])])
data b'{"text": "32373561303231626266623634383965353464343731383939663764623964313636336663363935656332666532613263343533386161626636353166643066"}'
headers Host: localhost:37176
User-Agent: python-requests/2.31.0
Accept-Encoding: gzip, deflate
Accept: */*
Connection: keep-alive
X-Authorization: fake
Content-Length: 140

get:

127.0.0.1 - - [29/Apr/2024 15:54:19] "GET /endpoint?{"text":%20"32373561303231626266623634383965353464343731383939663764623964313636336663363935656332666532613263343533386161626636353166643066"} HTTP/1.1" 200 -
values CombinedMultiDict([ImmutableMultiDict([]), ImmutableMultiDict([])])
data b'{"text": "32373561303231626266623634383965353464343731383939663764623964313636336663363935656332666532613263343533386161626636353166643066"}'
headers Host: localhost:37176
User-Agent: python-requests/2.31.0
Accept-Encoding: gzip, deflate
Accept: */*
Connection: keep-alive
X-Authorization: fake
Content-Length: 140

This probably deserves better testing at some point.

[leondz]

Great. Thanks for also updating restdemo.json, good catch