Convert tests that parse a BasicConstraints value to instead
parse an entire Certificate.
(Part of a series of changes for simplifying the parsing tests to be in
terms of just certificates for consistent entry point and expectations)
BUG=
634443
Committed:
https://crrev.com/07f7dafbfff3d483be66ddd85e1ed516f162e744
Cr-Commit-Position: refs/heads/master@{#420524}