Auto merge of #36072 - arthurprs:binary_heap_opt, r=Aatch
Auto merge of #36072 - arthurprs:binary_heap_opt, r=Aatch

Optimize BinaryHeap bounds checking

I was experimenting with d-ary binary heaps during the weekend (dead end) and I found that we could get some good improvements by removing bounds checking. Specially due to the panic-safe additional code, llvm can't really optimize them out.

```
 name                         d_ary_heap:: ns/iter  std___heap:: ns/iter  diff ns/iter  diff %
 bench_build_insert           148,610               236,960                     88,350  59.45%
 bench_from_vec               243,846               299,719                     55,873  22.91%
 bench_insert_2000_empty      4,512                 7,517                        3,005  66.60%
 bench_insert_2000_prefilled  28,665                32,605                       3,940  13.74%
 bench_pop_2000               111,515               128,005                     16,490  14.79%
 bench_pop_all                2,759,945             3,317,626                  557,681  20.21%
 peek_mut                     23,186                23,635                         449   1.94%
 pop_modify_push              41,573                43,822                       2,249   5.41%

test d_ary_heap::bench_build_insert          ... bench:     148,610 ns/iter (+/- 10,687)
test d_ary_heap::bench_from_vec              ... bench:     243,846 ns/iter (+/- 16,500)
test d_ary_heap::bench_insert_2000_empty     ... bench:       4,512 ns/iter (+/- 136)
test d_ary_heap::bench_insert_2000_prefilled ... bench:      28,665 ns/iter (+/- 1,347)
test d_ary_heap::bench_pop_2000              ... bench:     111,515 ns/iter (+/- 104,677)
test d_ary_heap::bench_pop_all               ... bench:   2,759,945 ns/iter (+/- 173,838)
test d_ary_heap::peek_mut                    ... bench:      23,186 ns/iter (+/- 106,254)
test d_ary_heap::pop_modify_push             ... bench:      41,573 ns/iter (+/- 3,313)
test std___heap::bench_build_insert          ... bench:     236,960 ns/iter (+/- 16,955)
test std___heap::bench_from_vec              ... bench:     299,719 ns/iter (+/- 6,354)
test std___heap::bench_insert_2000_empty     ... bench:       7,517 ns/iter (+/- 372)
test std___heap::bench_insert_2000_prefilled ... bench:      32,605 ns/iter (+/- 2,433)
test std___heap::bench_pop_2000              ... bench:     128,005 ns/iter (+/- 11,787)
test std___heap::bench_pop_all               ... bench:   3,317,626 ns/iter (+/- 238,968)
test std___heap::peek_mut                    ... bench:      23,635 ns/iter (+/- 1,420)
test std___heap::pop_modify_push             ... bench:      43,822 ns/iter (+/- 3,788)
```

Test code: https://github.com/arthurprs/heap-experiments

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