feat(bench): add BenchContext::start() and BenchContext::end() (#18734)

Closes #17589.
```ts
Deno.bench("foo", async (t) => {
  const resource = setup(); // not included in measurement
  t.start();
  measuredOperation(resource);
  t.end();
  resource.close(); // not included in measurement
});
```

1 files changed, 6 insertions, 0 deletions

diff --git a/cli/tests/integration/bench_tests.rs b/cli/tests/integration/bench_tests.rs
index 0ba297e63..73d541aa6 100644
--- a/cli/tests/integration/bench_tests.rs
+++ b/cli/tests/integration/bench_tests.rs
@@ -181,6 +181,12 @@ itest!(check_local_by_default2 {
   exit_code: 1,
 });
 
+itest!(bench_explicit_start_end {
+  args: "bench --quiet -A bench/explicit_start_and_end.ts",
+  output: "bench/explicit_start_and_end.out",
+  exit_code: 1,
+});
+
 itest!(bench_with_config {
   args: "bench --config bench/collect/deno.jsonc bench/collect",
   exit_code: 0,