MDEV-24487 Error after update to 10.5.8 on CentOS-8: DBD::mysql::st execute failed: Unknown MySQL error

The problem happened because the the new client capability flag
CLIENT_EXTENDED_METADATA was not put into the cache entry key.
So results cached by a new client were sent to the old client (and vica versa)
with a mis-matching metadata, which made the client abort the connection on
an unexpected result set metadata packet format.

The problem was caused by the patch for:
  MDEV-17832 Protocol: extensions for Pluggable types and JSON, GEOMETRY
which forgot to adjust the query cache code.

Fix:

- Adding a new member Query_cache_query_flags::client_extended_metadata,
  so only clients with equal CLIENT_EXTENDED_METADATA flag values can
  reuse results.

- Adding a new column CLIENT_EXTENDED_METADATA into
  INFORMATION_SCHEMA.QUERY_CACHE_INFO (privided by the qc_info plugin).