Rollup merge of #78621 - solson:inline, r=m-ou-se

Inline Default::default() for atomics

Functions like `AtomicUsize::default()` are not cross-crate inlineable before this PR ([see assembly output here](https://play.rust-lang.org/?version=stable&mode=release&edition=2018&gist=e353321766418f759c69fb141d3732f8)), which can lead to unexpected performance issues when initializing a large array using this function, e.g. as seen [here](https://github.com/spacejam/sled/blob/d513996a85875be8c813fd0e30a548b89682289a/src/histogram.rs#L53) which should turn into a simple loop writing zeroes but doesn't.

r? @m-ou-se