Improve {Set,Map}.fromAscList and friends

[meooow25]

Following up on #949 (comment)

This PR is based off #962, so marking as draft.

This PR improves

• Set.fromAscList, Set.fromDescList
• Map.fromAscList, Map.fromDescList, Map.fromAscListWith, Map.fromDescListWith, Map.fromAscListWithKey, Map.fromDescListWithKey

by making the combine function they use a good consumer and producer in terms of fusion. This gets rid of the intermediate list always created today, and also fuses with the input list if possible.

---

Benchmarks on GHC 9.2.5:

Before

Set
  fromAscList:         OK (0.20s)
    50.1 μs ± 2.9 μs, 240 KB allocated, 2.4 KB copied, 8.0 MB peak memory
  fromAscList:fusion:  OK (0.19s)
    89.5 μs ± 5.7 μs, 528 KB allocated, 6.8 KB copied, 8.0 MB peak memory
  fromDescList:        OK (0.22s)
    51.2 μs ± 2.9 μs, 240 KB allocated, 2.4 KB copied, 8.0 MB peak memory
  fromDescList:fusion: OK (0.18s)
    88.9 μs ± 5.7 μs, 559 KB allocated, 7.3 KB copied, 8.0 MB peak memory

Map
  fromAscList:         OK (0.18s)
    41.9 μs ± 3.6 μs, 343 KB allocated, 5.2 KB copied,  10 MB peak memory
  fromAscList:fusion:  OK (0.13s)
    63.0 μs ± 6.0 μs, 792 KB allocated,  15 KB copied,  10 MB peak memory
  fromDescList:        OK (0.17s)
    40.5 μs ± 3.9 μs, 343 KB allocated, 5.5 KB copied,  10 MB peak memory
  fromDescList:fusion: OK (0.25s)
    63.1 μs ± 5.3 μs, 824 KB allocated,  16 KB copied,  10 MB peak memory

After

Set
  fromAscList:         OK (0.18s)
    21.3 μs ± 1.4 μs, 128 KB allocated, 1.4 KB copied, 8.0 MB peak memory, 57% less than baseline
  fromAscList:fusion:  OK (0.89s)
    13.3 μs ± 221 ns, 144 KB allocated, 1.9 KB copied, 8.0 MB peak memory, 85% less than baseline
  fromDescList:        OK (0.18s)
    20.9 μs ± 1.6 μs, 128 KB allocated, 1.5 KB copied, 8.0 MB peak memory, 59% less than baseline
  fromDescList:fusion: OK (0.23s)
    13.7 μs ± 737 ns, 144 KB allocated, 2.0 KB copied, 8.0 MB peak memory, 84% less than baseline

Map
  fromAscList:        OK (0.22s)
    25.5 μs ± 2.0 μs, 152 KB allocated, 2.1 KB copied,  10 MB peak memory, 39% less than baseline
  fromAscList:fusion: OK (0.30s)
    18.0 μs ± 677 ns, 232 KB allocated, 4.3 KB copied,  10 MB peak memory, 71% less than baseline
  fromDescList:        OK (0.21s)
    25.1 μs ± 1.4 μs, 152 KB allocated, 2.1 KB copied,  10 MB peak memory, 38% less than baseline
  fromDescList:fusion: OK (0.20s)
    50.2 μs ± 3.1 μs, 577 KB allocated,  11 KB copied,  10 MB peak memory, 20% less than baseline

Some observations:

• There is no allocations penalty (unlike Improve {Set,Map}.fromDistinct{Asc,Desc}List #950), likely because we rid of the intermediate list and avoid a lot of allocations there.
• Map's fromDescList:fusion improves but not as much as fromAscList:fusion. The cause seems be that fusion with [n,n-1..1] does not work out as well as [1..n], but I don't know why and didn't dig into it much.

[meooow25]

Closing because this approach does not accommodate functions like mapKeys.
I plan to implement this differently (see #1027 (comment)).