Add warning messages when algorithms are skipped in autotune benchmarking

When algorithms exceed maxtime during benchmarking, they are correctly skipped
for larger matrix sizes. However, users only saw the initial "exceeded maxtime"
warning but not when algorithms were subsequently skipped, making it unclear
why some algorithms weren't being tested on larger matrices.

This adds explicit warning messages when algorithms are skipped, providing
better visibility into the autotuning process.

Fixes the issue where users would see:
- "Algorithm X exceeded maxtime" warnings
- But no indication that Algorithm X was being skipped for larger sizes

Now users will see both:
- "Algorithm X exceeded maxtime (Y.Zs > maxtime) for size N"
- "Algorithm X skipped for size M (exceeded maxtime on size N matrix)"

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

Co-Authored-By: Claude <[email protected]>

Author: ChrisRackauckas

lib/LinearSolveAutotune/src/benchmarking.jl

@@ -148,6 +148,7 @@ function benchmark_algorithms(matrix_sizes, algorithms, alg_names, eltypes;
                     if haskey(blocked_algorithms[string(eltype)], name)
                         max_allowed_size = blocked_algorithms[string(eltype)][name]
                         if n > max_allowed_size
+                            @warn "Algorithm $name skipped for size $n (exceeded maxtime on size $max_allowed_size matrix)"
                             # Still need to update progress bar
                             ProgressMeter.next!(progress)
                             # Record as skipped due to exceeding maxtime on smaller matrix