[Collections] add new commonest stdlib function

[drkameleon]

See also: (@BNAndras)

• https://discord.com/channels/765519132186640445/829324913097048065/1328209062684393482
• https://discord.com/channels/765519132186640445/829324913097048065/1328379332040593459
• https://discord.com/channels/765519132186640445/829324913097048065/1328399358613389434

The functionality is apparently related to mode in statistics, but since it's merely about finding "common" elements in a block, set or whatever, why wouldn't we simply include it in the Collections module? 🤔

[BNAndras]

What if it takes an optional predicate like maximum does? Then the user could define how they want to compare elements. That makes it a candidate for the Iterators module.

[drkameleon]

What if it takes an optional predicate like maximum does? Then the user could define how they want to compare elements. That makes it a candidate for the Iterators module.

That could be too. Although given Arturo's nature and the difference in arity between the two versions, we'd have to choose one of the two (whether it's a "normal" function operating on blocks, or an "iterator" with the usual syntax), or have them both - but with different names...

[BNAndras]

I think the iterator would be more useful since taking a predicate would give it more utility when the user can customize the behavior especially with dealing with custom types. The version that would just work on blocks could be approximated by using tally and grabbing the key with the highest score so it's a weaker candidate for the standard library.