Add a .str.find_many with AhoCorasick (similar to extract_many)

[jpfeuffer]

Description

I love your new"ish" .str.extract_many.
However, I would have assumed that a find_many (that returns the first start position of each of the matches) was actually the much more useful and more general method.
I barely ever had use case where I would need my (string literal!) patterns returned but had many use cases where I wanted to know the positions of those matches.

In any case, I am not saying that extract_many should go but would love to see a find_many equivalent.

It actually sounds relatively easy and I might consider it as a first Rust project that I could look at with some help. If you consider it a worthy addition.

I have not found a similar issue/request so far.

[jpfeuffer]

Similar to: #17304
Changes would just be to not use the "push" method and return the start indices:

polars/crates/polars-ops/src/chunked_array/strings/find_many.rs

Line 63 in e9a66e3

fn push(val: &str, builder: &mut ListStringChunkedBuilder, ac: &AhoCorasick, overlapping: bool) {

[jpfeuffer]

That's awesome. Thank you so much for the quick implementation @ritchie46