Find and fix deprecated APIs in k6

[mostafa]

This PR fixes deprecated APIs errors while running k6 (#38) and replaces them with the new APIs from k6 modules. The only issue with the changes is that SASL PLAIN/SCRAM doesn't seem to work. I'll fix this issue, and then I'll merge this PR.

I retested with the old API, and I noticed no difference or improvements in performance overall. It could be that the evolution of the kafka-go library and updating the k6 caused this massive speedup (expand and see below) compared to the original test in the README.

xk6-kafka is faster now? 🤔

The new changes made the extension more than 3x faster on fast-data-dev containers:

          /\      |‾‾| /‾‾/   /‾‾/
     /\  /  \     |  |/  /   /  /
    /  \/    \    |     (   /   ‾‾\
   /          \   |  |\  \ |  (‾)  |
  / __________ \  |__| \__\ \_____/ .io

  execution: local
     script: scripts/test_json.js
     output: -

  scenarios: (100.00%) 1 scenario, 50 max VUs, 1m30s max duration (incl. graceful stop):
           * default: 50 looping VUs for 1m0s (gracefulStop: 30s)


running (1m00.2s), 00/50 VUs, 9653 complete and 0 interrupted iterations
default ✓ [======================================] 50 VUs  1m0s

     ✓ is sent
     ✓ 10 messages returned

     █ teardown

     checks.........................: 100.00% ✓ 974953       ✗ 0
     data_received..................: 0 B     0 B/s
     data_sent......................: 0 B     0 B/s
     iteration_duration.............: avg=311.24ms min=33.87µs med=301.12ms max=767.25ms p(90)=354.48ms p(95)=385.52ms
     iterations.....................: 9653    160.396792/s
     kafka.reader.dial.count........: 50      0.830813/s
     kafka.reader.error.count.......: 0       0/s
     kafka.reader.fetches.count.....: 50      0.830813/s
     kafka.reader.message.bytes.....: 19 MB   315 kB/s
     kafka.reader.message.count.....: 96580   1604.798737/s
     kafka.reader.rebalance.count...: 0       0/s
     kafka.reader.timeouts.count....: 0       0/s
     kafka.writer.dial.count........: 150     2.49244/s
     kafka.writer.error.count.......: 0       0/s
     kafka.writer.message.bytes.....: 422 MB  7.0 MB/s
     kafka.writer.message.count.....: 1930600 32079.358475/s
     kafka.writer.rebalance.count...: 0       0/s
     kafka.writer.write.count.......: 1930600 32079.358475/s
     vus............................: 50      min=50         max=50
     vus_max........................: 50      min=50         max=50

and 4x faster on a bare Zookeeperless instance of Apache Kafka (v3.1.0 on Scala v2.13), compared to the previous results:

          /\      |‾‾| /‾‾/   /‾‾/
     /\  /  \     |  |/  /   /  /
    /  \/    \    |     (   /   ‾‾\
   /          \   |  |\  \ |  (‾)  |
  / __________ \  |__| \__\ \_____/ .io

  execution: local
     script: scripts/test_json.js
     output: -

  scenarios: (100.00%) 1 scenario, 50 max VUs, 1m30s max duration (incl. graceful stop):
           * default: 50 looping VUs for 1m0s (gracefulStop: 30s)


running (1m00.1s), 00/50 VUs, 13598 complete and 0 interrupted iterations
default ✓ [======================================] 50 VUs  1m0s

     ✓ is sent
     ✓ 10 messages returned

     █ teardown

     checks.........................: 100.00% ✓ 1373398      ✗ 0
     data_received..................: 0 B     0 B/s
     data_sent......................: 0 B     0 B/s
     iteration_duration.............: avg=220.82ms min=28.5µs med=215.94ms max=987.93ms p(90)=248.22ms p(95)=258.71ms
     iterations.....................: 13598   226.195625/s
     kafka.reader.dial.count........: 50      0.831724/s
     kafka.reader.error.count.......: 0       0/s
     kafka.reader.fetches.count.....: 50      0.831724/s
     kafka.reader.message.bytes.....: 27 MB   444 kB/s
     kafka.reader.message.count.....: 136030  2262.787977/s
     kafka.reader.rebalance.count...: 0       0/s
     kafka.reader.timeouts.count....: 0       0/s
     kafka.writer.dial.count........: 132     2.195751/s
     kafka.writer.error.count.......: 0       0/s
     kafka.writer.message.bytes.....: 595 MB  9.9 MB/s
     kafka.writer.message.count.....: 2719600 45239.125059/s
     kafka.writer.rebalance.count...: 0       0/s
     kafka.writer.write.count.......: 2719600 45239.125059/s
     vus............................: 50      min=50         max=50
     vus_max........................: 50      min=50         max=50

Update:
I couldn't figure out how to test SASL (no SSL), and I need someone to test it against a working instance of Kafka with SASL PLAIN/SCRAM enabled. I'll merge this, but won't release it until I fully test it. This means that you can test the feature by compiling with the latest commits on the main branch, but it won't be available as binary and a Docker image yet.