fix(perf): resolve concrete EP for the analyzer instead of ep=None (#931)

[xieofxie]

Summary

Fixes #931.

In winml perf without --ep, the EP was never resolved before the build, so the static analyzer ran with ep=None and aggregated across all EPs (logging analyze_onnx called with ep=None — results will aggregate all EPs), even though inference runs on a single device's EP.

This resolves a concrete device + EP from the request and passes it down to the build:

• PerfBenchmark resolves device + EP internally (_resolve_device_ep), at the start of _load_model so an unavailable/invalid combo fails fast before the export/optimize/quantize/compile pipeline runs (previously it only surfaced at session.compile()). BenchmarkConfig keeps only the raw request; the resolved values live on the instance and drive from_pretrained/from_onnx.
• _perf_modules derives a concrete EP from the resolved device when none is given. Explicit EPs are kept verbatim (downstream stages normalize aliases).
• The CLI perf() no longer pre-resolves — it just builds the config and dispatches.

WinMLAutoModel stays permissive: ep=None remains a valid library mode (aggregate across EPs). The fix makes perf — which targets one device — always pass an explicit EP, which is what the analyzer warning asked for.

Verification

End-to-end A/B on a real CPU build (--no-skip-build, no --ep):

	analyzer target	ep=None warning
before	None on cpu	fires
after	OpenVINOExecutionProvider on cpu	gone

Unit tests (tests/unit/commands/test_perf_cli.py, test_perf_module.py, 51 passed) cover: derived concrete EP reaches from_onnx; explicit EP passes through verbatim; an unavailable combo raises before the build is kicked off.

Follow-up

#939 tracks folding _perf_modules into PerfBenchmark so the two resolution sites become one.

[DingmaomaoBJTU]

Clean fix. The EP resolution logic is correct, idempotent, and placed at the right point (before the expensive build pipeline). Tests cover all the important cases: derived EP reaches from_onnx, explicit EP passes verbatim, unavailable combo fails fast. One minor nit: when resolve_eps returns [], _resolved_ep silently stays None — a comment making that invariant explicit would help future readers.