JIT: Add a simple Counter dumpable (#98350)

This allows easily measuring and outputting a single value at the end of
all JIT compilations.

src/coreclr/jit/compiler.hpp

@@ -294,6 +294,19 @@ class Dumpable
     virtual void dump(FILE* output) = 0;
 };
 
+// Helper class record and display a simple single value.
+class Counter : public Dumpable
+{
+public:
+    int64_t Value;
+
+    Counter(int64_t initialValue = 0) : Value(initialValue)
+    {
+    }
+
+    void dump(FILE* output);
+};
+
 // Helper class to record and display a histogram of different values.
 // Usage like:
 // static unsigned s_buckets[] = { 1, 2, 5, 10, 0 }; // Must have terminating 0

src/coreclr/jit/utils.cpp

@@ -1098,6 +1098,11 @@ void ConfigDoubleArray::Dump()
 
 #if CALL_ARG_STATS || COUNT_BASIC_BLOCKS || COUNT_LOOPS || EMITTER_STATS || MEASURE_NODE_SIZE || MEASURE_MEM_ALLOC
 
+void Counter::dump(FILE* output)
+{
+    fprintf(output, "%lld\n", (long long)Value);
+}
+
 /*****************************************************************************
  *  Histogram class.
  */