add contains (argument flipped occursin)

[oxinabox]

closes #35031
See issue for discussion.

Includes curried form per convention in #35052

in 2.0 we may want to remove occursin

[JeffBezanson]

Triage is ok with this.

[oxinabox]

Is this ready for merge?

[oxinabox]

bump

[oxinabox]

bump

[musm]

Thanks for this!

[o314]

Does this really a different function than in ?
Now, we have

using Test
@test 6 |> in(1:10)
@test "JuliaLang" |> startswith(r"Julia|Romeo")
@test_broken "aba" |> in(r"a.a") # will throw
@test "aba" |> contains(r"a.a")

Why do we not allow ?

using Test
using Test
@test 6 |> in(1:10)
@test "JuliaLang" |> startswith(r"Julia|Romeo")
@test"aba" |> in(r"a.a")

[oxinabox]

In is for elements, contains is for substrings.

[o314]

It is not in the essence of multidispatch to specialize function name according to type. Then we can talk for hours of what is a type.
If it is about subsetting there is issubset.
There is already in, but also issubset, occursin the badly named ismatch.
Adding one at time more and more naming - close, but not exactly the same, but how much, not sure - kill slowly the power of multidispatch .