refactor: change batch_size to request_size

[JoanFM]

Breaking Change #1606

[github-actions]

Latency summary

Current PR yields:

• 😶 index QPS at 1581, delta to last 3 avg.: +0%
• 😶 query QPS at 27, delta to last 3 avg.: -2%

Breakdown

Version	Index QPS	Query QPS
current	1581	27
0.9.13	1580	27
0.9.12	1576	27

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

[codecov]

Codecov Report

Merging #1677 (7cd59c5) into master (bfef4f0) will decrease coverage by 0.22%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1677      +/-   ##
==========================================
- Coverage   84.39%   84.17%   -0.23%     
==========================================
  Files         132      132              
  Lines        6831     6830       -1     
==========================================
- Hits         5765     5749      -16     
- Misses       1066     1081      +15     

Impacted Files	Coverage Δ
jina/helloworld/__init__.py	100.00% <ø> (ø)
jina/parsers/flow.py	100.00% <ø> (ø)
jina/peapods/runtimes/asyncio/grpc/async_call.py	93.75% <ø> (ø)
jina/clients/base.py	80.00% <100.00%> (ø)
jina/clients/request.py	91.66% <100.00%> (ø)
jina/clients/websockets.py	95.23% <100.00%> (ø)
jina/optimizers/flow_runner.py	100.00% <100.00%> (ø)
jina/parsers/client.py	100.00% <100.00%> (ø)
jina/parsers/helloworld.py	100.00% <100.00%> (ø)
jina/peapods/runtimes/jinad/api.py	75.65% <0.00%> (-9.87%)	⬇️

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