User/mishrak/add support for extended stats metrics

[Kritika1128]

Add Extended Statistics Support to ORT Perf Test Tool

Summary
Add support for a new -es command-line flag to the ORT Perf test tool that enables extended latency statistics output i.e., P75 latency, mean latency, and standard deviation. The -es flag requires -s to be enabled first — it extends the existing statistics output.
Additionally, updated README documentation to reflect the new -es flag and corrected the -s flag description to accurately list the percentiles it reports (P50, P90, P95, P99, P999). Also fixed a typo in the sample output (se -> sec).

Points to note

• -es is optional and depends on -s: Extended stats are not computed or shown unless both flags are enabled, keeping the default output unchanged.
• Extended stats positioned for readability: P75 is inserted between P50 and P90 (chronological order), and mean/standard deviation appear after P999 as summary metrics.

Files

• Modified: onnxruntime/test/perftest/README.md, onnxruntime/test/perftest/command_args_parser.cc, onnxruntime/test/perftest/performance_runner.cc, onnxruntime/test/perftest/performance_runner.h, onnxruntime/test/perftest/test_configuration.h

Validation Results

• Only -s flag is specified -> Outputs only existing statistics output

• Both -s and -es flag is specified ->Outputs both existing and extended statistics output