Replace once_cell::sync::Lazy with std::cell::LazyCell once it's stable

[neysofu]

We depend on once_cell for initialization of static items in the sov_schema_db crate, but we may be able to remove that dependency as std has std::cell::LazyCell, which is functionally equivalent (still unstable, though). While we could opt-in into the feature with #![feature(lazy_cell)], I don't really see a point –we wouldn't even remove once_cell from our dependency tree, just as a direct dependency– but let's make a note of switching away from once_cell when std has everything we need stabilized.

[citizen-stig]

That would be good idea, but we need to wait for stabilization #29

Do you have link to RFC about it, so we can easily track when it lands on stable?

[citizen-stig]

rust-lang/rust#109736

[kzhui125]

LazyLock stabilized in 1.80