[backend/frontend] can upload file from markdown editor (#7281)

[esrevi]

Proposed changes

• MarkdownField update: importing file image <= 5Mb directly by paste, drop or browse an image, and set at the cursor position
• Store the image in the storage/embedded/[entity]
• Update opencti_stix2 on client python to transform a embedded link storage to a data base64 image
• On importing, after draft approval, transform the images in base64 to file, store them at the right place, and return a storage link

Related issues

• Resolves Be able to easily copy/paste images, upload etc. in markdown editor (+ more capabilities) #7281

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case (coverage and e2e)
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

[codecov]

Codecov Report

❌ Patch coverage is 65.78658% with 311 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.56%. Comparing base (2c2809d) to head (7501828).
⚠️ Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
...latform/opencti-graphql/src/manager/syncManager.js	0.00%	96 Missing ⚠️
...latform/opencti-graphql/src/database/middleware.ts	49.70%	86 Missing ⚠️
...i-graphql/src/database/middlewareEmbeddedImages.ts	58.72%	71 Missing ⚠️
...i-graphql/src/database/markdown-embedded-images.ts	87.43%	47 Missing ⚠️
client-python/pycti/utils/opencti_stix2.py	88.54%	11 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #15556       +/-   ##
===========================================
+ Coverage   33.44%   67.56%   +34.12%     
===========================================
  Files        3188      952     -2236     
  Lines      216129   104208   -111921     
  Branches    39858     9114    -30744     
===========================================
- Hits        72283    70410     -1873     
+ Misses     143846    33798   -110048     

Flag	Coverage Δ
opencti-client-python	46.18% <88.54%> (+0.58%)	⬆️
opencti-front	?
opencti-graphql	70.19% <63.09%> (+0.23%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.