[docs] refactor some conic tutorials into simple_examples.jl

[odow]

We've done this for things like https://jump.dev/JuMP.jl/stable/tutorials/nonlinear/simple_examples/, so we might as well do it here too. I don't think we're going to refactor this into much larger examples with verbose descriptions.

Preview: https://jump.dev/JuMP.jl/previews/PR3229/tutorials/conic/simple_examples/

Part of #2348

[codecov]

Codecov Report

Base: 98.07% // Head: 98.07% // No change to project coverage 👍

Coverage data is based on head (74a3ea1) compared to base (eae58d2).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3229   +/-   ##
=======================================
  Coverage   98.07%   98.07%           
=======================================
  Files          34       34           
  Lines        4632     4632           
=======================================
  Hits         4543     4543           
  Misses         89       89           

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