This commit introduces variants test-ca_utf8.crt,
test-ca_printablestring.crt and test-ca_uppercase.crt
of tests/data_files/test-ca.crt which differ from
test-ca.crt in their choice of string encoding and
upper and lower case letters in the DN field. These
changes should be immaterial to the recovation check,
and three tests are added that crl.pem, which applies
to test-ca.crt, is also considered as applying to
test-ca_*.crt.

The test files were generated using PR #1641 which
- adds a build instruction for test-ca.crt to
  tests/data_files/Makefile which allows easy
  change of the subject DN.
- changes the default string format from `PrintableString`
  to `UTF8String`.

Specifically:
- `test-ca_utf8.crt` was generated by running
      `rm test-ca.crt && make test-ca.crt`
   on PR #1641.
- `test-ca_uppercase.crt`, too, was generated by running
      `rm test-ca.crt && make test-ca.crt`
   on PR #1641, after modifying the subject DN line in the build
   instruction for `test-ca.crt` in `tests/data_files/Makefile`.
-  `test-ca_printable.crt` is a copy of `test-ca.crt`
   because at the time of this commit, `PrintableString` is
   still the default string format.