fix(docker): *-dev tags target right stage from Dockerfile

[lodu]

Fixes this issue

SUMMARY

the Dockerfile contains a dev stage but this is not the stage that is targeted when building and releasing the *-dev tags (e.g.: master-dev on Docker Hub.
This PR fixes said behaviour, and also adds a test case for this issue.

TESTING INSTRUCTIONS

tox -- ./tests/unit_tests/scripts/docker_build.py
or
pytest ./tests/unit_tests/scripts/docker_build.py

ADDITIONAL INFORMATION

• Has associated issue: Docker *-dev tag's are not targetting the dev stage of Dockerfile #27111
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (13f1642) 67.16% compared to head (eec1fdf) 67.16%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #27116   +/-   ##
=======================================
  Coverage   67.16%   67.16%           
=======================================
  Files        1900     1900           
  Lines       74444    74444           
  Branches     8296     8296           
=======================================
  Hits        50002    50002           
  Misses      22387    22387           
  Partials     2055     2055           

Flag	Coverage Δ
mysql	78.02% <ø> (ø)
postgres	78.12% <ø> (ø)
python	78.26% <ø> (ø)
sqlite	77.64% <ø> (ø)

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