fix(simulation): correct exponential sampling and cache behavior logic

- Fixed incorrect use of exponential sampling for `next_request` and `next_refresh` timings.
- Adjusted cache eviction logic to properly handle capacity checks.
- Improved simulation output and logging for least accessed objects.
- Corrected CSV export to include index labels for better data clarity.
- Reran experiments

Signed-off-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>

experiments/README.md

@@ -6,6 +6,8 @@ Explanation for files in each experiment:
 - `hit_age.csv`: Shows hit rate/average age at time of request for each object.
 - `lambda_distribution.pdf`: Lambda Distribution across all objects/discrete
   values of the Zipf distribution
+- `lambda_vs_access_count.pdf`: Displays the access count against lambda,
+  expecting a higher lambda to result in a higher access count.
 - `objects_in_cache_over_time.pdf`: Amount of cache entries at given time.
 - `overall_hit_age.csv`: Cumulative description of `hit_age.csv`