Get all GitHub Actions jobs passing again.
There are no Ubuntu 18.04 runners in GitHub Actions anymore, so use
22.04.
Update mk/* scripts to match what's in *ring*'s main branch;
some of these changes are required for Ubuntu 22.04. This also fixes
a typo in the invocation of `cargo clippy`.
Temporarily allow `clippy::explicit_auto_deref` to avoid source code
changes prior to the next 0.22.1 release. Tweak `dns_names_test.rs`
so that it doesn't trigger `clippy::octal_escapes` false positives.
Update `cargo deny` to the latest release and update deny.toml so
that the Unicode license will be accepted, matching *ring*'s
configuration.
Test all feature configurations in CI.
Remove the `trust_anchor_utils` feature flag.
Guard all features that directly require allocation with a new `alloc` feature.
The RSA features will be handled separately.
Document the features. Tell docs.rs to document all features.
Adjust some tests so that tests are run in more configurations.
Unless/until we adapt all the tests to use wasm-bindgen-test, no tests are
actually run. In fact the jobs succeed even if there are missing symbols
from *ring*!
Brian Smith