Explain 6110's deferred-fence count and record its corpus costs

Corpus 6110 has three statements with no static lowering, and its
@deferred-fences directive is 9 because coverage counts each lowering of a
wrapper body: the .call and .apply wrapper bodies are each lowered four
times. The program's header now says so. The commit also adds the
program's corpus-costs entries, which shard balancing reads.

tests/corpus/6110-cjs-speculative-wrapper-fences.cjs

@@ -4,6 +4,9 @@
 // every statement of their bodies. A statement with no static lowering
 // (here `module.exports` read as a value) compiles to its runtime fence
 // instead of vanishing; these never run, so the binary matches Node.
+// Coverage counts the three fenced statements nine times: each lowering of
+// a wrapper body counts its statements, and the `.call` and `.apply`
+// wrapper bodies are each lowered four times.
 const verbose = process.argv.length > 99;
 (function () {
   var root = this;

tests/harness/corpus-costs.json

@@ -2217,6 +2217,7 @@
     "6104-typeof-builtin-bindings.mjs": 2031,
     "6105-cjs-top-level-this/main.js": 1371,
     "6106-esm-top-level-this.mjs": 1915,
+    "6110-cjs-speculative-wrapper-fences.cjs": 1980,
     "6140-cjs-require-tdz-throws/main.js": 2731,
     "6141-cjs-require-tdz-checked/main.js": 2856,
     "6142-cjs-require-published-early/main.js": 3400,
@@ -5256,6 +5257,7 @@
     "6104-typeof-builtin-bindings.mjs": 1715,
     "6105-cjs-top-level-this/main.js": 3213,
     "6106-esm-top-level-this.mjs": 1672,
+    "6110-cjs-speculative-wrapper-fences.cjs": 2500,
     "6140-cjs-require-tdz-throws/main.js": 2989,
     "6141-cjs-require-tdz-checked/main.js": 4062,
     "6142-cjs-require-published-early/main.js": 5156,