Fix shell script execution and config bugs

[ammaarrahmed]

Fixes for Benchmark Execution Scripts #5

This update resolves several critical bugs in the execution workflow that were affecting test reliability and data collection.

1. Fixed Zenoh Benchmark Exit Code Muting

• Issue: In both run_single_process_benchmark.sh and run_multi_process_benchmark.sh, the benchmark's exit code was being clobbered by the subsequent kill ${ROUTER_PID} command. If irobot_benchmark failed but the kill succeeded, the failure was silently ignored and the suite advanced.
• Fix: The benchmark's exit code is now explicitly captured (local benchmark_exit_code=$?) before the Zenoh cleanup block, ensuring failures are correctly caught and the script aborts.

2. Fixed Incorrect Variable Unset Syntax

• Issue: The scripts used unset $ROUTER_PID (which evaluates the variable first, e.g., unset 12345) instead of unset ROUTER_PID. This is a no-op that leaves the PID variable defined, causing the next iteration's cleanup conditional to attempt killing the old, now defunct PID. This could potentially terminate unrelated processes on the host.
• Fix: Corrected to unset ROUTER_PID.

3. Added Missing --results-dir to Multi-Process Runner

• Issue: The run_multi_process_benchmark.sh script lacked the --results-dir argument, causing irobot_benchmark to dump logs in the current working directory /ws instead of the targeted output folder. The script then relied on a fragile mv ./*log "$RESULT_FOLDER" glob, which caused errors in the SystemLatencyLogger during cleanup.
• Fix: Added --results-dir ${RESULT_FOLDER} to the execution command, aligning it with the single-process runner and removing the race condition.

4. Applied Zenoh Router Custom Configs

• Issue: run_zenoh_router.sh loaded ZENOH_ROUTER_CONFIG_URI from the test matrix, but never actually passed it to the rmw_zenohd process. As a result, custom session configurations (like the critical timeout reductions documented in the CHANGELOG) were never applied, causing the router to trigger repeated "scouting delay" warnings.
• Fix: Exported ZENOH_ROUTER_CONFIG_URI into the environment before launching rmw_zenohd so the RMW implementation picks it up.

5. Corrected Minor Config Typo

• Fix: Updated the header comment in memory_test.conf which incorrectly stated it was for ActionClient/ActionServer mix process benchmarks instead of memory benchmarks.