test_runner: skip branches entirely on ignored lines

Fixes: #61586

When a branch is entirely on ignored lines (via c8 ignore comments),
it should not appear in the BRDA output at all, rather than appearing
with 0 coverage.

Modified the branch coverage logic to check if all lines in the branch
are ignored before adding to branchReports and incrementing totalBranches.
This ensures ignored branches don't pollute coverage reports.

Author: drtootsie

lib/internal/test_runner/coverage.js

@@ -193,18 +193,20 @@ class TestCoverage {
           ObjectAssign(range, mapRangeToLines(range, lines));
 
           if (isBlockCoverage) {
-            ArrayPrototypePush(branchReports, {
-              __proto__: null,
-              line: range.lines[0]?.line,
-              count: range.count,
-            });
-
-            if (range.count !== 0 ||
-                range.ignoredLines === range.lines.length) {
-              branchesCovered++;
+            // Skip branches that are entirely on ignored lines
+            if (range.ignoredLines !== range.lines.length) {
+              ArrayPrototypePush(branchReports, {
+                __proto__: null,
+                line: range.lines[0]?.line,
+                count: range.count,
+              });
+
+              if (range.count !== 0) {
+                branchesCovered++;
+              }
+
+              totalBranches++;
             }
-
-            totalBranches++;
           }
         }