IPA: validate conflicts with other installers, return proper error

[mna]

Related issue: Resolves #36621

Checklist for submitter

• Changes file added for user-visible changes in changes/, orbit/changes/ or ee/fleetd-chrome/changes.
  See Changes files for more information.

• Input data is properly validated, SELECT * is avoided, SQL injection is prevented (using placeholders for values in statements)

Testing

• Added/updated automated tests

• Where appropriate, automated tests simulate multiple hosts and test for host isolation (updates to one hosts's records do not affect another)

• QA'd all new/changed functionality manually

[codecov]

Codecov Report

❌ Patch coverage is 68.69565% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.81%. Comparing base (5059107) to head (d79296f).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
server/datastore/mysql/software_installers.go	52.38%	10 Missing and 10 partials ⚠️
server/datastore/mysql/vpp.go	60.00%	7 Missing and 5 partials ⚠️
server/datastore/mysql/in_house_apps.go	90.47%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #38005      +/-   ##
==========================================
- Coverage   65.81%   65.81%   -0.01%     
==========================================
  Files        2386     2386              
  Lines      190086   190171      +85     
  Branches     8323     8323              
==========================================
+ Hits       125108   125152      +44     
- Misses      53597    53620      +23     
- Partials    11381    11399      +18     

Flag	Coverage Δ
backend	67.65% <68.69%> (-0.01%)	⬇️

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