[GPU] Improve max-allocation error guidance and enable_large_allocations docs

[Sahilbhatane]

Details:

• When a single allocation exceeds the device max allocation size, engine::check_allocatable() fails with an assertion. The message had a small formatting issue (missing space before "Please") and didn’t point users to the GPU_ENABLE_LARGE_ALLOCATIONS / ov::intel_gpu::hint::enable_large_allocations workaround.
• Updated the error message in src/plugins/intel_gpu/src/runtime/engine.cpp to fix the spacing and include a clear suggestion to enable GPU_ENABLE_LARGE_ALLOCATIONS when applicable.
• Aligned the internal option description in src/plugins/intel_gpu/include/intel_gpu/runtime/options.inl with the actual behavior. The check is against the device max allocation size, not just “>4GB”.
• Extended the public property documentation in src/inference/include/openvino/runtime/intel_gpu/properties.hpp to clarify that enabling large allocations also bypasses the max-allocation-size check, which helps when a single buffer exceeds CL_DEVICE_MAX_MEM_ALLOC_SIZE.
• These changes are limited to user-facing messages and documentation. Validation was done by reviewing the updated text across all affected files.

Tickets:

• [Build]: [GPU] Max single allocation size exceeded when compiling OpenVINO model on Intel GPU #34856

AI Assistance:

• AI assistance used: yes/partially
• AI was used for issue triage, tracing the config/property flow through the codebase, and helping draft this PR description. All code and documentation changes were applied and reviewed manually in the repository.

[Copilot]

Pull request overview

Improves Intel GPU plugin user-facing guidance around failures caused by a single allocation exceeding the device’s maximum allocatable buffer size, and clarifies the behavior of the enable_large_allocations option/property in internal and public docs.

Changes:

• Update the max-allocation assertion message to fix formatting and point users to GPU_ENABLE_LARGE_ALLOCATIONS.
• Align the internal option description for ov::intel_gpu::hint::enable_large_allocations with the real check (device max allocation size rather than “>4GB”).
• Clarify the public property documentation to mention bypassing the max-allocation-size check and its usefulness when exceeding CL_DEVICE_MAX_MEM_ALLOC_SIZE.

Reviewed changes

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

File	Description
src/plugins/intel_gpu/src/runtime/engine.cpp	Improves the assertion text for “single allocation exceeds device max alloc size” and adds a workaround hint.
src/plugins/intel_gpu/include/intel_gpu/runtime/options.inl	Updates the option help text to describe the behavior more accurately than the previous “>4GB” wording.
src/inference/include/openvino/runtime/intel_gpu/properties.hpp	Extends the public property doxygen to document bypassing the max-alloc-size check and relates it to CL_DEVICE_MAX_MEM_ALLOC_SIZE.

[p-durandin]

build_jenkins

[Sahilbhatane]

@p-durandin Re-requesting build. Updated the branch, all checks passed on previous build.