Fix cube materialization for cubes with derived metrics

[shangyian]

Summary

Cubes containing derived ratio metrics failed with 'NoneType' object is not subscriptable because those metrics weren't being returned by the v3 measures-SQL builder.

The fix is to register derived metrics on their grain group. The v3 builder tracks derived metrics in BuildContext.decomposed_metrics but doesn't list them in any GrainGroupSQL.metrics. The v2-shape adapter
_v3_grain_group_to_measures_query now also walks decomposed_metrics and registers any derived metric whose components are fully covered by this grain group's components, so downstream build_cube_materialization can emit a CubeMetric for it.

Also added a defensive error for missing-metric-mapping. If a cube metric isn't in the built metrics_mapping, raise a descriptive DJInvalidInputException naming the missing metric(s) instead of crashing with NoneType is not subscriptable deeper in the comprehension.

Test Plan

• PR has an associated issue: #
• make check passes
• make test shows 100% unit test coverage

Deployment Plan

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