Consolidate repeat code in TBE inference

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Summary: - Consolidate some repeat code in TBE inference for int64 indices enablement

Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request was exported from Phabricator. Differential Revision: D61734479

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This pull request has been merged in pytorch/FBGEMM@d5452932ec513d49461588e3cbdeb7e95fbc4618.