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/record_unpack.myc

@@ -2,7 +2,8 @@
 ;; This test calls a function that destructures a record 100.000 times.
 ;; Current implementation is now zero-allocation for destructuring.
 ;; Output: {:a 1, :b 2}
-;; Benchmark: 5.3ms
+;; Benchmark: 5.2ms
+
 (do
   (def process (fn [[x y]] 
     (+ x y)))