feat: DbuApplication stub relocation

[RobPasMue]

Description

Moves the DbuApplication stub to the new gRPC architecture

Issue linked

Related to #1817

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate unit tests.
• I have reviewed my changes before submitting this pull request.
• I have linked the issue or issues that are solved to the PR if any.
• I have assigned this PR to myself.
• I have added the minimum version decorator to any new backend method implemented.
• I have made sure that the title of my PR follows Conventional commits style (e.g. feat: extrude circle to cylinder)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.38%. Comparing base (305c074) to head (2bd589d).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1882      +/-   ##
==========================================
+ Coverage   90.29%   90.38%   +0.09%     
==========================================
  Files         102      105       +3     
  Lines        9304     9330      +26     
==========================================
+ Hits         8401     8433      +32     
+ Misses        903      897       -6     

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[b-matteo]

All good!