Rollup merge of #72628 - MikailBag:array-default-tests, r=shepmaster
Rollup merge of #72628 - MikailBag:array-default-tests, r=shepmaster

Add tests for 'impl Default for [T; N]'

Related: #71690.
This pull request adds two tests:
- Even it T::default() panics, no leaks occur.
- [T; 0] is Default even if T is not.

I believe at some moment `Default` impl for arrays will be rewritten to use const generics instead of macros, and these tests will help to prevent behavior changes.

graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust