bench: Add the `room_list` bench

[Hywan]

Example of the output:

room_list/sync/10       time:   [3.5673 ms 3.5899 ms 3.6181 ms]
                        thrpt:  [2.7639 Kelem/s 2.7856 Kelem/s 2.8032 Kelem/s]
Found 12 outliers among 100 measurements (12.00%)
  1 (1.00%) low severe
  3 (3.00%) high mild
  8 (8.00%) high severe
room_list/sync/100      time:   [3.6342 ms 3.6667 ms 3.7037 ms]
                        thrpt:  [27.000 Kelem/s 27.273 Kelem/s 27.516 Kelem/s]
Found 12 outliers among 100 measurements (12.00%)
  5 (5.00%) high mild
  7 (7.00%) high severe
room_list/sync/1000     time:   [30.426 ms 30.611 ms 30.810 ms]
                        thrpt:  [32.457 Kelem/s 32.668 Kelem/s 32.867 Kelem/s]
Found 20 outliers among 100 measurements (20.00%)
  13 (13.00%) high mild
  7 (7.00%) high severe
Benchmarking room_list/sync/10000: Warming up for 3.0000 s
Warning: Unable to complete 100 samples in 5.0s. You may wish to increase target time to 35.7s, or reduce sample count to 10.
room_list/sync/10000    time:   [353.56 ms 355.14 ms 356.97 ms]
                        thrpt:  [28.014 Kelem/s 28.158 Kelem/s 28.284 Kelem/s]
Found 5 outliers among 100 measurements (5.00%)
  3 (3.00%) high mild
  2 (2.00%) high severe

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 84.86%. Comparing base (8865e2f) to head (ebd0242). Report is 369 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3661      +/-   ##
==========================================
- Coverage   84.89%   84.86%   -0.03%     
==========================================
  Files         272      272              
  Lines       29167    29167              
==========================================
- Hits        24761    24753       -8     
- Misses       4406     4414       +8     

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[poljar]

We're not particularly interested in this as of now and this is bitrotting, so closing now. If we ever decide to benchmark this properly let's reopen.