Fix deprecated field names in MultistartOptimization result handling

Updates the `_local_optimiser` function in OptimizationMultistartOptimization
to use the current field names for optimization results:
- Changed `res.minimum` to `res.objective`
- Changed `res.minimizer` to `res.u`

This resolves deprecation warnings when running tests and ensures compatibility
with the current OptimizationSolution API.

The traits for MultistartOptimization.TikTak are already correctly set:
- `requiresbounds = true` (TikTak needs bounds for Sobol sequence generation)
- `allowsbounds = true` (TikTak passes bounds to local optimizer)

Fixes issue mentioned in https://discourse.julialang.org/t/error-when-using-multistart-optimization/133174

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ChrisRackauckas

lib/OptimizationMultistartOptimization/src/OptimizationMultistartOptimization.jl

@@ -62,7 +62,7 @@ function SciMLBase.__solve(cache::OptimizationBase.OptimizationCache{
     _local_optimiser = function (pb, θ0, prob)
         prob_tmp = remake(prob, u0 = θ0)
         res = solve(prob_tmp, cache.solver_args.local_opt)
-        return (value = res.minimum, location = res.minimizer, ret = res.retcode)
+        return (value = res.objective, location = res.u, ret = res.retcode)
     end
 
     local_optimiser(pb, θ0) = _local_optimiser(pb, θ0, cache.solver_args.prob)