Since aws-lc-rs doesn't support no-std it's moved from the default
features to the std features.

Similarly we must tweak our `once_cell` usage to provide the
`race` feature for builds without `std`.

See the upstream[0] docs section on "Does this crate support no_std?"
for some important caveats.

[0]: https://docs.rs/once_cell/latest/once_cell/

For no-std users, the new `ClientConfig::builder_with_details()` must
be used, which requires a `TimeProvider` implementation up-front.

For std builds, the `ClientConfig` uses the `DefaultTimeProvider` for
existing `ClientConfig::builder*` functions.

will be back in phase II

no-std users must use the new ServerConfig::builder_with_details(),
which requires a `TimeProvider` to be provided up-front.

For std builds, the `ServerConfig` uses the `DefaultTimeProvider`
for existing, other `ServerConfig::builder*` functions.

default Resumption to disabled

will be back in phase II

When built w/ the `std` feature, the `DEFAULT_CRYPTO_PROVIDER` and
assoc. fns use a standard `once_cell::sync::OnceCell`. When built w/o
the `std` feature we use `once_cell::race::OnceBox`, requiring some
minor adjustments to account for the expectation of storing
a `Box<Arc<CryptoProvider>>` in place of a `Arc<CryptoProvider>`.