Substitute HashMap for BtreeMap in family

[spoutn1k]

Updates #128, fixes #125.

Edit: updated numbers for 2026

     Running benches/baseline.rs (target/release/deps/baseline-afaf49df79a6aa37)
Gnuplot not found, using plotters backend
counter                 time:   [1.5237 ns 1.5238 ns 1.5240 ns]
                        change: [-0.1374% -0.0297% +0.0816%] (p = 0.61 > 0.05)
                        No change in performance detected.
Found 12 outliers among 100 measurements (12.00%)
  2 (2.00%) low mild
  2 (2.00%) high mild
  8 (8.00%) high severe

counter via family lookup
                        time:   [4.5786 ns 4.5919 ns 4.6077 ns]
                        change: [-1.3790% -1.0886% -0.7645%] (p = 0.00 < 0.05)
                        Change within noise threshold.
Found 4 outliers among 100 measurements (4.00%)
  3 (3.00%) high mild
  1 (1.00%) high severe

     Running benches/exemplars.rs (target/release/deps/exemplars-44e9e58bee91a180)
Gnuplot not found, using plotters backend
histogram without exemplars
                        time:   [5.2069 ns 5.2149 ns 5.2237 ns]
                        change: [-0.8447% -0.4973% -0.1840%] (p = 0.00 < 0.05)
                        Change within noise threshold.
Found 13 outliers among 100 measurements (13.00%)
  2 (2.00%) low mild
  4 (4.00%) high mild
  7 (7.00%) high severe

histogram with exemplars (no exemplar passed)
                        time:   [5.7712 ns 5.7765 ns 5.7835 ns]
                        change: [-2.3160% -2.0050% -1.6724%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 13 outliers among 100 measurements (13.00%)
  1 (1.00%) low mild
  10 (10.00%) high mild
  2 (2.00%) high severe

histogram with exemplars (some exemplar passed)
                        time:   [46.992 ns 47.047 ns 47.105 ns]
                        change: [-6.1891% -5.2597% -4.3480%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
  1 (1.00%) low mild
  4 (4.00%) high mild
  3 (3.00%) high severe

     Running benches/family.rs (target/release/deps/family-9fc0fb35439fee5b)
Gnuplot not found, using plotters backend
counter family with [(&'static str, &'static str)] label set
                        time:   [11.101 ns 11.173 ns 11.234 ns]
                        change: [-49.818% -49.403% -49.005%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 11 outliers among 100 measurements (11.00%)
  4 (4.00%) low severe
  3 (3.00%) low mild
  4 (4.00%) high mild

counter family with Vec<(&'static str, &'static str)> label set
                        time:   [19.108 ns 19.205 ns 19.315 ns]
                        change: [-36.874% -36.427% -35.912%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
  4 (4.00%) high mild
  4 (4.00%) high severe

counter family with Vec<(String, String)> label set
                        time:   [53.065 ns 53.165 ns 53.279 ns]
                        change: [-16.658% -16.289% -15.940%] (p = 0.00 < 0.05)
                        Performance has improved.
Found 7 outliers among 100 measurements (7.00%)
  3 (3.00%) high mild
  4 (4.00%) high severe

counter family with custom type label set
                        time:   [5.1398 ns 5.1493 ns 5.1596 ns]
                        change: [-44.652% -44.504% -44.337%] (p = 0.00 < 0.05)
                        Performance has improved.

     Running benches/histogram.rs (target/release/deps/histogram-cbf0fe399db614ec)
Gnuplot not found, using plotters backend
observe/histogram       time:   [4.6503 ns 4.6601 ns 4.6698 ns]
                        change: [-1.4986% -0.9936% -0.4452%] (p = 0.00 < 0.05)
                        Change within noise threshold.
Found 7 outliers among 100 measurements (7.00%)
  2 (2.00%) low severe
  4 (4.00%) low mild
  1 (1.00%) high mild
observe/native histogram
                        time:   [5.3982 ns 5.3994 ns 5.4005 ns]
                        change: [-0.7902% -0.6653% -0.5421%] (p = 0.00 < 0.05)
                        Change within noise threshold.
Found 18 outliers among 100 measurements (18.00%)
  2 (2.00%) low severe
  6 (6.00%) low mild
  3 (3.00%) high mild
  7 (7.00%) high severe
observe/classic and native histogram
                        time:   [5.6864 ns 5.6929 ns 5.7037 ns]
                        change: [-0.7474% -0.5332% -0.2340%] (p = 0.00 < 0.05)
                        Change within noise threshold.
Found 10 outliers among 100 measurements (10.00%)
  1 (1.00%) low severe
  2 (2.00%) low mild
  2 (2.00%) high mild
  5 (5.00%) high severe

     Running benches/encoding/text.rs (target/release/deps/text-742f9524329bef5c)
Gnuplot not found, using plotters backend
encode                  time:   [11.127 ms 11.169 ms 11.213 ms]
                        change: [+1.7567% +2.2668% +2.7645%] (p = 0.00 < 0.05)
                        Performance has regressed.
Found 8 outliers among 100 measurements (8.00%)
  5 (5.00%) high mild
  3 (3.00%) high severe