feat: add outside values to while loop argument list

[avik-pal]

This will likely fix the issue with tt that @giordano reported some time back.

[wsmoses]

@GleasonK i vaguely recall there being an existing stablehlo pass for this?

[github-actions]

EnzymeJAX Benchmarks

Benchmark suite	Current: 90beba7	Previous: f603104	Ratio
scatter_sum / JaX / cpu / Primal	0.0000042210789993987415 s	0.000004260189699562034 s	0.99
scatter_sum / JaXPipe / cpu / Primal	0.000004273433900380042 s	0.000004406429699884029 s	0.97
scatter_sum / JaX / tpu / Primal	0.0001627930903006 s	0.0001248841227003 s	1.30
scatter_sum / JaXPipe / tpu / Primal	0.0001470225415003 s	0.0001351668211995 s	1.09

This comment was automatically generated by workflow using github-action-benchmark.

[Pangoraw]

IT seems to be done during MLIR HLO to HLO conversion: https://github.com/openxla/xla/blob/c6315cd85539fac2c08ed33dbe25e006f41ce72b/xla/hlo/translate/mhlo_to_hlo/mlir_hlo_to_hlo.cc#L5053-L5065

[GleasonK]

We have:

• WhileOpImplicitCapture which takes constant arguments and converts them to implicit captures
• prepareExplicitCapturedConstants which takes implicit captures and moves the constant values into the while body as explicit captures

An improvement to the prepareExplicitCapture for whileop would be to only sink smaller constants or single-use constants into the while body, converting larger shared constants into arguments.