Bug #30316: Some "parts" tests fail because the server uses "--secure-file-priv"
Bug #30341: Test suite "parts" needs to be adapted to the new rules disallowing many functio
Bug #30408: Suite "parts" needs bug numbers updated
Bug #30411: Suite "parts" needs bug numbers updated: ER_UNIQUE_KEY_NEED_ALL_FIELDS_IN_PF
Bug #30576: part_supported_sql_func_innodb.test tries to LOAD DATA outside of var dir
Bug #30581: partition_value tests use disallowed CAST() function

Included are some general fixes to allow the "parts" test suite to be run
successfully.  This includes disabling a few tests or parts of tests,
cleaning up the test cases and their results, etc.  Basically, these tests
have not been run for some time, and had suffered some bit rot.

The bugs were fixed as a single changeset, because in some ways they depend
on each other.  I couldn't be sure I'd updated all the error codes (for
bugs 30408 and 30411) without also adapting to the new allowed functions
rules (bug 30341), and vice versa.