[clang] [Coverage] Introduce the type `CounterPair` for RegionCounterMap. NFC. (PR #112724)

[NAKAMURA Takumi via cfe-commits]

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@@ -101,6 +101,25 @@ enum ForDefinition_t : bool {
   ForDefinition = true
 };
 
+class CounterPair : public std::pair<uint32_t, uint32_t> {
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chapuni wrote:

Added comments, and refactored more.
- Introduce the subclass `ValueOpt` and move mask operations into it.
- Name the pair as `Executed` and `Skipped`. (I prefer `std::pair` though...)

https://github.com/llvm/llvm-project/pull/112724