injection_points: Tweak more permutation in isolation test "basic"

injection_points: Re-enable permutation in isolation test "basic"

injection_points: Improve comment about disabled isolation permutation

injection_points: Disable one permutation in isolation test "basic"

injection_points: Add basic isolation test

psql: Sprinkle more CppAsString2() in describe.c

pg_amcheck: Use CppAsString2() for relkind and relpersistence in queries