Add functions Array::find_first() and Array::get_first()

[matt08-prog]

implemented the function Array::find_custom as discussed in godotengine/godot-proposals#6006.

This is my first time making a PR for the codebase so I'm sure I missed some things. Thanks in advance.

• Bugsquad edit, closes: Add more array methods: first_custom, last_custom, count_custom godot-proposals#6889*

[idbrii]

Looks pretty good. Thanks for taking this on!

[Maran23]

Looking at the proposal, the idea is to return an element (Variant) of the Array, not an int...
And as also written in the proposal, I'm still in favor of naming it find_first/get_first, to provide the information to the caller that he will get in fact the first element, so the sort order is important.

[AThousandShips]

Reviewers, see also:

• Add Array.find_if()/rfind_if() methods #73490
• Add more array methods: find_custom, rfind_custom #80208

[akien-mga]

Superseded by #95449. Thanks for the contribution!

[Radivarig]

@akien-mga This PR implements Variant get_first which was not covered by the PR it was superseded by #95449.

I was looking forward to having an array method that returns the Variant directly. Can this be reopened please?