Support halve and decay for CountMinSketch

[tisonkun]

Ref -

• https://docs.rs/cmsketch/latest/cmsketch/struct.CMSketchU16.html

While migrating @MrCroxx's foyer from CMSketch to DataSketches' CountMinSketch, I noticed this gap.

Our implementation was initialized at:

• feat: implement count-min sketch #38
• Add count-min sketch datasketches-java#494
• Count-Min Sketch datasketches-go#42
• Cpp countmin datasketches-cpp#325

I wonder if halve and decay are part of the standard CountMin sketch and how we can implement it into datasketches-rust.

cc @PsiACE @jmalkin @c-dickens @geonove as original authors

[tisonkun]

Resolved by #71.