[StableHLO] Legalize composite ops to calls in the input pipeline (#24777)

The StableHLO input conversion pipeline had no handling for
`stablehlo.composite`, so any composite reaching the conversion to
Linalg failed with:
```
  error: failed to legalize operation 'stablehlo.composite' that was explicitly marked illegal
```

JAX emits composites for some CHLO operations, e.g.
```
  %0 = stablehlo.composite "chlo.acos" %arg0
      {decomposition = @chlo.acos.impl, version = 1 : i32}
      : (tensor<8x32xf32>) -> tensor<8x32xf32>
```
which made such models uncompilable.

Run `stablehlo-legalize-composite-to-call` early in the pipeline, right
after deserialization. It replaces each composite with a call to the
function holding its decomposition, which the inliner later in the
pipeline folds away, so the remaining conversions only ever see the
decomposed form. The pass is given an explicit empty exception list to
document where composites that should be preserved as a unit can be
opted out.

Signed-off-by: Paul Stark <paul.stark@cdprojektred.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>