Fix benchmarks in `escaping_benchmark.cc` by properly calling `benchmark::DoNotOptimize` on both inputs and outputs and by removing the unnecessary and wrong `ABSL_RAW_CHECK` condition (`check != 0`) of `BM_ByteStringFromAscii_Fail` benchmark.

Relevant comment:
```
// The DoNotOptimize(...) function can be used to prevent a value or
// expression from being optimized away by the compiler. This function is
// intended to add little to no overhead.
// See: http://stackoverflow.com/questions/28287064
//
// The specific guarantees of DoNotOptimize(x) are:
//  1) x, and any data it transitively points to, will exist (in a register or
//     in memory) at the current point in the program.
//  2) The optimizer will assume that DoNotOptimize(x) could mutate x or
//     anything it transitively points to (although it actually doesn't).
//
// To see this in action:
//
//   void BM_multiply(benchmark::State& state) {
//     int a = 2;
//     int b = 4;
//     for (auto s : state) {
//       testing::DoNotOptimize(a);
//       testing::DoNotOptimize(b);
//       int c = a * b;
//       testing::DoNotOptimize(c);
//     }
//   }
//   BENCHMARK(BM_multiply);
//
// Guarantee (2) applied to 'a' and 'b' prevents the compiler lifting the
// multiplication outside of the loop. Guarantee (1) applied to 'c' prevents the
// compiler from optimizing away 'c' as dead code.
```
To see #1 and #2 in action, see: https://godbolt.org/z/ned1578ve

PiperOrigin-RevId: 676588185
Change-Id: I7ed3e4bed8274b54ac7877316f2d82c33d68f00f