Update http snippets for restsharp 107+

[llimllib]

a whack at fixing #312

To test this, I:

• generated all new fixtures with OVERWRITE_EVERYTHING=true npm run test
• generated a C# hello world project with dotnet new console -o HelloWorld -f net7.0
• installed RestSharp into it with dotnet add package RestSharp]
• ran this script and looked for significant differences between csharp and bash:

#!/usr/bin/env bash
set -euxo pipefail
file=Program.cs
mkdir -p fixtures
# for the multipart tests
printf "hello" > hello.txt
for fixture in ~/readme/kong-httpsnippet/src/targets/csharp/restsharp/fixtures/*; do
    rm -f $file

    # the custom method isn't supported
    if [[ $fixture == *custom-method* ]]; then continue; fi

    printf "using RestSharp;\n\n" > $file
    sed 's,test/fixtures/files/hello.txt,hello.txt,' "$fixture" >> $file
    printf 'Console.WriteLine("{0}", response.Content);' >> $file

    dotnet run $file > "fixtures/$(basename "$fixture".out)"
done
#
# now run the bash fixtures for comparison
for fixture in ~/readme/kong-httpsnippet/src/targets/shell/curl/fixtures/*; do
    # the curl for custom-indentation does not work properly, so we need to add
    # || true
    sed 's,test/fixtures/files/hello.txt,hello.txt,' "$fixture" |
        bash > "fixtures/$(basename "$fixture".out)" || true
done

# then, compare the outputs
for fixture in ~/readme/kong-httpsnippet/kong-httpsnippet/src/targets/http/http1.1/fixtures/*; do
    base=$(basename "$fixture")
    cs="fixtures/$base.cs.out"
    sh="fixtures/$base.sh.out"

    if [[ ! -e $cs ]]; then printf "Unable to find fixture %s\n" "$cs"; continue; fi
    if [[ ! -e $cs ]]; then printf "Unable to find fixture %s\n" "$sh"; continue; fi

    git diff "fixtures/$base.cs.out" "fixtures/$base.sh.out" || true
done

[llimllib]

Closing here, fixed in readmeio/httpsnippet, here