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/macro_financial.myc

@@ -1,4 +1,5 @@
-;; Benchmark: 400ns
+;; Benchmark: 484ns
+;; Benchmark-Repeat: 4144
 ;; Financial DSL Macro example
 ;; Demonstrates generating complex records from simple parameters.
 ;; Output: {:price 100, :size 2, :total 200}