docs: use port replace port expose in client

[bwanglzu]

1. fixed all clients in docs from port_expose to port.
2. minor test change, test client test_independent_client is not testing client, it's testing flow.
3. remove coverage.rc since not used anymore, remove jina/hub from test config since hub is not a submodule of jina anymore. Added pytest.ini to ignore pytest.mark.slow warnings.

[codecov]

Codecov Report

Merging #3340 (ce549af) into master (b7797d7) will increase coverage by 0.99%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3340      +/-   ##
==========================================
+ Coverage   88.73%   89.73%   +0.99%     
==========================================
  Files         152      152              
  Lines       10812    10820       +8     
==========================================
+ Hits         9594     9709     +115     
+ Misses       1218     1111     -107     

Flag	Coverage Δ
daemon	45.61% <ø> (-0.05%)	⬇️
jina	89.72% <ø> (+1.44%)	⬆️

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

Impacted Files	Coverage Δ
jina/jaml/parsers/base.py	71.42% <0.00%> (-28.58%)	⬇️
jina/types/ndarray/__init__.py	80.00% <0.00%> (-10.91%)	⬇️
jina/types/ndarray/sparse/__init__.py	93.33% <0.00%> (-6.67%)	⬇️
jina/proto/jina_pb2_grpc.py	77.77% <0.00%> (-4.58%)	⬇️
jina/peapods/runtimes/base.py	87.09% <0.00%> (-2.91%)	⬇️
jina/optimizers/__init__.py	94.23% <0.00%> (-2.80%)	⬇️
jina/optimizers/flow_runner.py	95.45% <0.00%> (-2.22%)	⬇️
jina/peapods/runtimes/zmq/asyncio.py	92.98% <0.00%> (-1.57%)	⬇️
jina/optimizers/parameters.py	96.82% <0.00%> (-1.57%)	⬇️
jina/peapods/pods/k8s.py	70.79% <0.00%> (-1.28%)	⬇️
... and 23 more

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[github-actions]

Latency summary

Current PR yields:

• 🐎🐎 index QPS at 1228, delta to last 2 avg.: +7%
• 🐎🐎 query QPS at 49, delta to last 2 avg.: +6%
• 🐎🐎 dam extend QPS at 49659, delta to last 2 avg.: +8%
• 🐎🐎 avg flow time within 1.744 seconds, delta to last 2 avg.: +18%
• 🐢🐢 import jina within 0.3394 seconds, delta to last 2 avg.: -13%

Breakdown

Version	Index QPS	Query QPS	DAM Extend QPS	Avg Flow Time (s)	Import Time (s)
current	1228	49	49659	1.744	0.3394
2.0.23	1228	49	51892	1.6974	0.3605
2.0.22	1052	42	39651	1.2385	0.4267

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