[MetaSchedule] Add decompose point hint for RewriteReductionBlock

[vinx13]

This PR added an annotation meta_schedule.decompose_point as a hint for RewriteReductionBlock. When the outer reduction loop has extent of 1, it won't be recognized as reduction loops and decompose_reduction won't be used. In some cases like tensorization, the init block need to be tensorized. In this case, decompose_reduction is necessary and such hint is helpful.
As part of MultiLevelTilingTensorCore, the outermost reduction loop is annotated with such hint.

cc @junrushao @masahi

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• cc @Hzfengsy, @elvin-n, @junrushao _{See #10317 for details}

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[vinx13]

Closing this as #13579 is a better solution