[Docs] add missing arrayXYZ functions

[Blargian]

Closes #1934 as part of the functions project to document missing functions.

This PR adds documentation for the following functions listed in #1934:

• array → already exists as array(x1, …), operator [x1, …] here
• arrayDotProduct
• arrayEnumerateDenseRanked
• arrayEnumerateUniqRanked
• arrayFirstOrNull
• arrayFlatten → already exists here
• arrayLastOrNull
• arrayPartialShuffle
• arrayShuffle

Changelog category (leave one):

• Documentation (changelog entry is not required)

Documentation entry for user-facing changes

• Documentation is written (mandatory for new features)

[Blargian]

@justindeguzman @johnnymatthews could one of you please give this a look over when you get a chance.

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[rschu1ze]

Please document what N stands for (=the cardinality/size of the input array).

[rschu1ze]

It is not clear to the reader what this function is actually doing.

• [1..limit] is supposed to be a random (aka. shuffled) subset of the input array
• (limit..N] is supposed to be a random subset of the remaining elements.

So function arrayPartialShuffle basically permutes the whole thing? How is it then different from arrayShuffle?

[Blargian]

@rschu1ze I've tried to make it clearer what this function does - both in the description, and in the examples. How does it look to you now?

[rschu1ze]

It is better now, thank you!

[rschu1ze]

In of size N, "N" should be quoted.

(really minor, can be fixed in a follow-up PR)

[rschu1ze]

"The order" seems a remnant.