fix: add missing OrderedSet/unwrap imports in CasADi/Pyomo dynamic-opt exts

The `__init__` workaround added in 4888437 to fix a Julia 1.10 method
invalidation bug calls `OrderedSet{SymbolicT}()` and `unwrap(...)`, but
neither name is imported in `MTKCasADiDynamicOptExt` or
`MTKPyomoDynamicOptExt`. This causes the extensions to fail to load on
Julia 1.10 with `UndefVarError: OrderedSet not defined`, breaking the
LTS Extensions test job (`Rocket launch` test in
`test/extensions/dynamic_optimization.jl` is the visible failure).

`MTKInfiniteOptExt` had the same workaround but with the proper
`using OrderedCollections: OrderedSet` and `using Symbolics: unwrap`
imports, so it loads fine. Mirror those imports here.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

Author: ChrisRackauckas

lib/ModelingToolkitBase/ext/MTKCasADiDynamicOptExt.jl

@@ -4,7 +4,8 @@ using CasADi
 using DiffEqBase
 using UnPack
 using NaNMath
-using Symbolics: SymbolicT
+using OrderedCollections: OrderedSet
+using Symbolics: SymbolicT, unwrap
 const MTK = ModelingToolkitBase
 
 function __init__()

lib/ModelingToolkitBase/ext/MTKPyomoDynamicOptExt.jl

@@ -5,6 +5,8 @@ using DiffEqBase
 using UnPack
 using NaNMath
 using Setfield
+using OrderedCollections: OrderedSet
+using Symbolics: SymbolicT, unwrap
 import SymbolicUtils as SU
 const MTK = ModelingToolkitBase