Add flag to route ai gateway methods via rpc

[G4brym]

This property is purposely not documented

[codspeed-hq]

Merging this PR will degrade performance by 11.73%

❌ 1 regressed benchmark
✅ 69 untouched benchmarks
⏩ 129 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	Encode_ASCII_32[TextEncoder][0/0/32]	3.1 ms	3.5 ms	-11.73%

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_{Comparing G4brym:add-ai-gateway-flag-for-rpc (2d9f3d6) with main (8891c0f)}

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[jclee]

I'm not familiar with this particular feature, but I assume it's analogous to the previously merged PR #5995 that added the aiSearch() method.