perftest: Use plugin EP device allocators for input/output buffers

[Jaskaran Singh Nagi (jnagi-intel)]

Description

Adds support for using a plugin EP device's own allocator for input/output buffers in onnxruntime_perf_test, instead of always using the CPU allocator.

• When a session uses plugin EP(s) (--plugin_eps), onnxruntime_perf_test now selects an allocator from the appended OrtEpDevice: it prefers the device's default (device-only) allocator, falls back to its host-accessible allocator, and falls back to the CPU allocator if neither is available or if more than one EP device was appended (no single unambiguous allocator to pick).
• Generated inputs (-r) and pre-allocated fixed-shape outputs now use this allocator instead of the CPU allocator.
• Real test data loaded from files is staged into the selected allocator's memory once at load time (via Ort::Env::CopyTensor), instead of being copied per-Run() implicitly.
• String tensors are always kept in CPU-accessible memory (inputs and outputs), since std::string is placement-constructed by ORT directly into the tensor's owned memory and can't safely live in device-only memory.
• Added [Plugin EP]-prefixed logging indicating which allocator was selected.

Motivation and Context

onnxruntime_perf_test previously always allocated input/output buffers on the CPU when running with plugin EPs. For plugin EPs whose kernels expect device-resident inputs/outputs, this meant every Run() iteration paid for an implicit host↔device copy that was entirely avoidable, skewing per-iteration latency measurements away from the EP's actual compute cost. Selecting and reusing the EP device's own allocator up front lets perf numbers better reflect steady-state inference cost for plugin EPs.

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[Copilot]

Pull request overview

Updates perftest to select allocators exposed by plugin EP devices.

Changes:

• Returns selected plugin EP devices during session setup.
• Chooses a default or host-accessible plugin allocator.
• Falls back to the CPU allocator for ambiguous/unavailable devices.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
onnxruntime/test/perftest/utils.h	Declares plugin device and allocator-selection APIs.
onnxruntime/test/perftest/common_utils.cc	Implements selected-device tracking and allocator lookup.
onnxruntime/test/perftest/ort_test_session.cc	Applies the selected allocator to perftest buffers.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.