Improve instances code

[nesitor]

Problem: If an instance is created and removed, one of the base mounted devices remains on the system. Also, a user cannot create a Qemu disk from Debian image.

Solution: Remove the useless device from the system and create the two needed script to create Qemu Debian runtimes.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 59.97%. Comparing base (45c14c5) to head (08eb1f4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #654      +/-   ##
==========================================
+ Coverage   59.94%   59.97%   +0.02%     
==========================================
  Files          64       64              
  Lines        5458     5459       +1     
  Branches      592      592              
==========================================
+ Hits         3272     3274       +2     
- Misses       2043     2044       +1     
+ Partials      143      141       -2     

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[olethanh]

lgtm