Replace OnceLock with LazyLock

[russellbanks]

LazyLock is simpler than OnceLock and the docs suggest its use over OnceLock in simple cases where different initializers based on the caller are not required:

In many simple cases, you can use LazyLock<T, F> instead to get the benefits of this type with less effort: LazyLock<T, F> “looks like” &T because it initializes with F on deref! Where OnceLock shines is when LazyLock is too simple to support a given case, as LazyLock doesn’t allow additional inputs to its function after you call LazyLock::new(|| ...).

OnceCell was used in #160 (and therefore #179) as it became stable in v1.70 whilst LazyLock became stable in v1.80. With the MSRV bump of keyring v4 to v1.85, this is no longer a consideration.

[brotskydotcom]

Looks great, thanks a lot!