Rollup merge of #154929 - davidgauch:const-default-lazy, r=jhpratt

Add `const Default` impls for `LazyCell` and `LazyLock`

Follow up to these commits by @estebank rust-lang/rust#134628 and rust-lang/rust#151190.
Tracking issue rust-lang/rust#143894.

cc @fmease @fee1-dead @oli-obk

This enables `static L: LazyLock<D> = Default::default()`  for any type `D: Default` which is safe as `D::default()` is only evaluated at runtime.

Author: JonathanBrouwer