feat: Expose Executors as first class citizens

[jacobowitz]

Expose Executors as first class citizens

Description

This adds to_k8s_yaml() and to_docker_compose_yaml() for the Executors. It works similar to serve() in the sense that it creates a Flow behind the scenes and uses its existing methods to provide a similar user experience.
These features are also added to the docs and some basic tests have been added.

• Implement to_k8s_yaml() and to_docker_compose_yaml() as a static convenience wrapper for Executors
• Update the docs: Executors can now be deployed via the k8s/docker-compose mechanism. Explain the difference between external/shared Executors.

Closes # (4502)

[github-actions]

Latency summary

Current PR yields:

• 🐎🐎🐎🐎 index QPS at 1292, delta to last 2 avg.: +17%
• 🐎🐎🐎🐎 query QPS at 76, delta to last 2 avg.: +29%
• 🐢🐢 avg flow time within 1.1495 seconds, delta to last 2 avg.: -20%
• 🐢🐢 import jina within 0.4077 seconds, delta to last 2 avg.: -12%

Breakdown

Version	Index QPS	Query QPS	Avg Flow Time (s)	Import Time (s)
current	1292	76	1.1495	0.4077
3.2.10	1264	72	1.6016	0.3838
3.2.9	933	44	1.2827	0.5481

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

[codecov]

Codecov Report

Merging #4597 (25d12e2) into master (5e0ee17) will decrease coverage by 1.87%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4597      +/-   ##
==========================================
- Coverage   87.70%   85.83%   -1.88%     
==========================================
  Files         117      117              
  Lines        8411     8479      +68     
==========================================
- Hits         7377     7278      -99     
- Misses       1034     1201     +167     

Flag	Coverage Δ
jina	85.83% <100.00%> (-1.85%)	⬇️

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

Impacted Files	Coverage Δ
jina/orchestrate/flow/base.py	89.78% <100.00%> (-0.10%)	⬇️
jina/serve/executors/__init__.py	85.44% <100.00%> (+0.72%)	⬆️
jina/helloworld/multimodal/app.py	0.00% <0.00%> (-88.14%)	⬇️
jina/helloworld/multimodal/my_executors.py	69.79% <0.00%> (-27.52%)	⬇️
jina/serve/networking.py	76.53% <0.00%> (-9.23%)	⬇️
jina/serve/runtimes/head/__init__.py	83.70% <0.00%> (-8.73%)	⬇️
jina/types/mixin.py	62.50% <0.00%> (-6.25%)	⬇️
jina/types/request/data.py	92.92% <0.00%> (-5.06%)	⬇️
jina/clients/request/__init__.py	69.56% <0.00%> (-4.35%)	⬇️
.../runtimes/request_handlers/data_request_handler.py	89.47% <0.00%> (-3.51%)	⬇️
... and 11 more

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[github-actions]

📝 Docs are deployed on https://feat-executor-first-class--jina-docs.netlify.app 🎉