tests: Remove 'make extra-tests' rule.
tests: Add new 'make check-all' rule.

This runs all of the check* rules.  Since this includes 'make check',
'make check-all' is not quite equivalent to the old 'make extra-tests'
which was removed in the previous commit.
tests: Add 'make check-release' rule.

This is a subset of tests which will be required to pass before a
tarball can be released by the maintainer.