refactor: clean up replica set

[jacobowitz]

Closes https://github.com/jina-ai/internal-tasks/issues/370

We had both head_args and the head itself in the ReplicaSet. Both is redundant. We need the head so I removed the head_args and get them from the head instead

[github-actions]

Latency summary

Current PR yields:

• 🐢🐢 index QPS at 1029, delta to last 2 avg.: -21%
• 🐢🐢 query QPS at 18, delta to last 2 avg.: -17%
• 🐢🐢 dam extend QPS at 28537, delta to last 2 avg.: -17%
• 🐢🐢 avg flow time within 1.5458 seconds, delta to last 2 avg.: +15%
• 🐎🐎🐎🐎 import jina within 0.4893 seconds, delta to last 2 avg.: +14%

Breakdown

Version	Index QPS	Query QPS	DAM Extend QPS	Avg Flow Time (s)	Import Time (s)
current	1029	18	28537	1.5458	0.4893
2.6.4	1231	22	33125	1.1402	0.4377
2.6.3	1398	21	35889	1.5402	0.4133

Backed by latency-tracking. Further commits will update this comment.

[codecov]

Codecov Report

Merging #4141 (08d3dc3) into master (3976695) will increase coverage by 0.82%.
The diff coverage is 90.00%.

@@            Coverage Diff             @@
##           master    #4141      +/-   ##
==========================================
+ Coverage   86.55%   87.37%   +0.82%     
==========================================
  Files         125      120       -5     
  Lines        9644     8697     -947     
==========================================
- Hits         8347     7599     -748     
+ Misses       1297     1098     -199     

Flag	Coverage Δ
daemon	42.25% <43.97%> (-7.28%)	⬇️
jina	84.77% <87.42%> (+2.45%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
jina/excepts.py	100.00% <ø> (ø)
jina/helloworld/chatbot/app.py	82.97% <ø> (-0.70%)	⬇️
jina/parsers/peapods/pea.py	100.00% <ø> (ø)
jina/parsers/peapods/pod.py	100.00% <ø> (ø)
jina/parsers/ping.py	100.00% <ø> (ø)
jina/peapods/peas/container_helper.py	73.80% <ø> (ø)
jina/peapods/runtimes/base.py	74.19% <ø> (-6.46%)	⬇️
jina/proto/jina_pb2.py	58.10% <46.55%> (-41.90%)	⬇️
jina/peapods/runtimes/__init__.py	61.11% <55.55%> (+4.58%)	⬆️
jina/peapods/pods/k8s.py	80.66% <74.13%> (+1.11%)	⬆️
... and 69 more

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