script: Replace raw pointer comparison with == for DOM identity comparison - #46718

Unlike claimed in
servo#46678 (comment) and
servo#46718, the result from benchmark is
counter-intuitive.
`std::ptr::eq` is actually 15% slower than
https://github.com/servo/servo/blob/fc340087b7411d5d736ad8705581baf16b567b1c/components/dom_struct/lib.rs#L154-L156.

The benchmark mimics the one used in
servo#35323.

Testing: 
`.\mach exec cargo bench -p servo-script-bindings`
```
Running benches.rs (target\release\deps\dom_partial_eq-8ef5af22310fd8f7.exe)
ptr_eq_same             time:   [598.35 ps 602.22 ps 606.18 ps]
Found 4 outliers among 100 measurements (4.00%)
  1 (1.00%) low mild
  1 (1.00%) high mild
  2 (2.00%) high severe

ptr_eq_different        time:   [615.17 ps 619.21 ps 623.09 ps]
Found 3 outliers among 100 measurements (3.00%)
  1 (1.00%) high mild
  2 (2.00%) high severe

dom_eq_same             time:   [514.00 ps 519.76 ps 525.78 ps]
Found 5 outliers among 100 measurements (5.00%)
  3 (3.00%) high mild
  2 (2.00%) high severe

dom_eq_different        time:   [514.45 ps 520.22 ps 526.39 ps]
Found 6 outliers among 100 measurements (6.00%)
  1 (1.00%) low mild
  4 (4.00%) high mild
  1 (1.00%) high severe
```

Also, production profile `.\mach exec cargo bench --profile production
-p servo-script-bindings` is always slower than default.

---------

Signed-off-by: Euclid Ye <yezhizhenjiakang@gmail.com>