Update benchmark timings and repeats

This commit updates the benchmark timings and repeat counts for various
example files. The `tester.rs` script has been modified to:

- Correctly parse and use the `Benchmark-Repeat` directive.
- Implement an adaptive sampling mechanism for more accurate median
  calculation, especially for long-running benchmarks.
- Improve the logic for updating and inserting benchmark and repeat
  lines in example files.
- Handle potential compilation and runtime errors during benchmark
  execution.

examples/data.myc

@@ -1,5 +1,6 @@
 ;; Complex Data Structure Test
-;; Benchmark: 51.4us
+;; Benchmark: 52.9us
+;; Benchmark-Repeat: 39
 ;; Output: {:name "Fibonacci", :input 10, :output 55}
 (do
   (def fib (fn [n]