Implement ranges::merge#1101

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StephanTLavavej merged 3 commits intomicrosoft:masterfrom

CaseyCarter:merge

Aug 5, 2020

Commits on Jul 28, 2020

Implement ranges::merge
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Commits on Jul 29, 2020

STL's review comment
CaseyCarter
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Commits on Aug 5, 2020

Miya's review comments
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