[clang] [llvm] [MC/DC] Refactor: Introduce `ConditionIDs` as `std::array<2>` (PR #81221)

[NAKAMURA Takumi via cfe-commits]

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@@ -217,6 +217,9 @@ class CounterExpressionBuilder {
 
 using LineColPair = std::pair<unsigned, unsigned>;
 
+using MCDCConditionID = unsigned int;
+using MCDCConditionIDs = std::array<MCDCConditionID, 2>;
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chapuni wrote:

`first` and `second` didn't make sense to me.

https://github.com/llvm/llvm-project/pull/81221