Details:
  - Limit the queries to character sets and collations
    which are most probably available in all build types.
    But try to preserve the intention of the tests.
  - Remove the variants adjusted to some build types.

  Note:
  1. The results of the review by Bar are included.
  2. I am not able to check the correctness of this patch
     on any existing build type and any MySQL version.
     So it could happen that the new test fails somewhere.