[Kernel SDK] Function for verifying a DAC certificate

Context

Currently there is no function in the Kernel SDK for verifying a certificate against a threshold value of signatures, and the list of public keys for committee members. This is implemented in the current MR.

Closes #5482 (closed)

Manually testing the MR

make -f kernels.mk build
make -f kernels.mk test
make -f kernels.mk check

verified that all certificate tests are executed when running make -f kernels.mk test

test dac::certificate::tests::encode_decode_certificate ... ok
test dac::certificate::tests::verify_invalid_certificate_insufficient_signatures ... ok
test dac::certificate::tests::verify_valid_certificate ... ok
test dac::certificate::tests::verify_invalid_certificate_wrong_signature ... ok

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR