Move custom lists pydantic model into models package

[jonathangreen]

Description

Move the custom lists controllers pydantic models into the palace.manager.api.admin.model package.

Motivation and Context

I moved these while working on #2186 because I thought I would be able to reuse them. Turns out the work editor uses different data, so I couldn't reuse them. I think it makes sense though to move these, so they are with the rest of the admin controller pydantic models.

How Has This Been Tested?

• Running tests

Checklist

• I have updated the documentation accordingly.
• All new and existing tests passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.03%. Comparing base (64b5368) to head (d5ceeb8).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2187      +/-   ##
==========================================
+ Coverage   90.93%   91.03%   +0.10%     
==========================================
  Files         362      363       +1     
  Lines       41222    41225       +3     
  Branches     8850     8850              
==========================================
+ Hits        37487    37531      +44     
+ Misses       2441     2421      -20     
+ Partials     1294     1273      -21     

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