Add find filters to optimize where-first chains

[ashmaroli]

• This is a 🙋 feature or enhancement.
• I've added tests.
• I've adjusted the documentation.

Summary

Introducing Liquid filters find and find_exp to optimize scenarios involving first chained to where and where_exp filter respectively.

Purpose

where (where_exp) evaluates given conditions against all items in a given array and chaining the first filter returns a single object from the pool. This could be wasteful when the array is large with numerous items and the first winner is near the starting end.

i.e. say the array is ["apple", "lemonade", "spade", "sunglasses", "umbrella", "cola"]
{{ array | where: "type", "drink" | first }} and {{ array | find: "type", "drink" }} are equivalent and return the same object ("lemonade") but the latter stops processing after two items.

[DirtyF]

What's the expected gain?

If liquid don't have it, why should we?
https://shopify.github.io/liquid/filters/where/

[ashmaroli]

Is that something that already exists in Liquid?

As of now, there is no find filter in upstream Liquid.

What's the expected gain?

For the general user-base? Depends on how it is used.
For Jekyll's docs site, profiles for #8172 should shed some light.

[ashmaroli]

I've added a benchmark script to compare the performance of the find filter vs where + first filters to illustrate the possible boost.

[ashmaroli]

If liquid don't have it, why should we?

@DirtyF Liquid has a different implementation of where filter from ours. So even if they were to add a find filter, it would be based on their version of where. That could have a different outcome for our users.

[DirtyF]

According to the profile docs tests, this brings a significant improvement for build time 👍

[DirtyF]

@jekyll: merge +minor