We have upgraded to go1.24.1 in production, and no longer need to test
go1.23.x. Updating the version in our go.mod also allows us to begin
using x509.Certificate.Policies instead of .PolicyIdentifiers.
In go1.17, the `x509.CreateCertificate()` method fails if the provided
Signer (private key) and Parent (cert with public key) do not match.
This change both updates the lint library to create and use an issuer
cert whose public key matches the throwaway private key used for lint
signatures, and overhauls its public interface for readability and
simplicity.
Rename the `lint` library to `linter`, to allow other methods to be
renamed to reduce word repetition. Reduce the linter library interface
to three functions: `Check()`, `New()`, and `Linter.Check()` by making
all helper functions private. Refactor the top-level `Check()` method to
rely on `New()` and `Linter.Check()` behind the scenes. Finally, create
a new helper method for creating a lint issuer certificate, call this
new method from `New()`, and store the result in the `Linter` struct.
Part of #5480
Aaron Gable