Rollup merge of #127709 - Zalathar:pair-mod, r=Nadrieril

match lowering: Move `MatchPair` tree creation to its own module

This makes it easier to see that `MatchPair::new` has only one non-recursive caller, because the recursive callers are all in this module. No functional changes.

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I have used `git diff --color-moved` to verify that the moved code is identical to the old code, except for reduced visibility on the helper methods.

0 files changed, 0 insertions, 0 deletions