feat: add additional metrics

[samsja]

linked to #4731

add new metrics

• Request size: In bytes of the request object
• Number of pending requests: gateway only

SKIP

• (skip to do in another PR) Number of fails: How many requests failed, exception type etc
• (skip to do in another PR) Number of Clients connected: gateway only

[codecov]

Codecov Report

Merging #4789 (7357a9a) into master (f0f5948) will increase coverage by 0.24%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4789      +/-   ##
==========================================
+ Coverage   88.01%   88.26%   +0.24%     
==========================================
  Files         119      119              
  Lines        9012     9031      +19     
==========================================
+ Hits         7932     7971      +39     
+ Misses       1080     1060      -20     

Flag	Coverage Δ
jina	88.26% <100.00%> (+0.31%)	⬆️

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

Impacted Files	Coverage Δ
jina/serve/runtimes/gateway/request_handling.py	96.29% <100.00%> (+0.21%)	⬆️
.../runtimes/request_handlers/data_request_handler.py	94.57% <100.00%> (+0.21%)	⬆️
...a/orchestrate/deployments/config/docker_compose.py	99.00% <0.00%> (-1.00%)	⬇️
jina/orchestrate/flow/base.py	89.56% <0.00%> (-0.48%)	⬇️
jina/helper.py	81.75% <0.00%> (+0.02%)	⬆️
jina/hubble/helper.py	89.29% <0.00%> (+1.29%)	⬆️
jina/serve/runtimes/gateway/http/__init__.py	100.00% <0.00%> (+2.22%)	⬆️
jina/types/mixin.py	72.91% <0.00%> (+4.16%)	⬆️
jina/orchestrate/deployments/__init__.py	91.14% <0.00%> (+4.45%)	⬆️

---

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[github-actions]

Latency summary

Current PR yields:

• 🐎🐎🐎🐎 index QPS at 1513, delta to last 2 avg.: +47%
• 🐎🐎🐎🐎 query QPS at 85, delta to last 2 avg.: +65%
• 🐎🐎🐎🐎 avg flow time within 1.4864 seconds, delta to last 2 avg.: +11%
• 🐢🐢 import jina within 0.41 seconds, delta to last 2 avg.: -29%

Breakdown

Version	Index QPS	Query QPS	Avg Flow Time (s)	Import Time (s)
current	1513	85	1.4864	0.41
3.4.4	984	49	1.3694	0.6252
3.4.3	1073	53	1.2997	0.5425

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

[JoanFM]

Some tests should be added

[samsja]

Some tests should be added

I added integration tests for both of the current metrics

[github-actions]

📝 Docs are deployed on https://feat-new-metrics--jina-docs.netlify.app 🎉