prepared statement caching enablement

there is a difference between 2.x and 3.x :
In 2.x caching is enable by option cachePrepStmts (default true) when useServerPrepStmts is enable (default false), while in 3.x, it's only enable with cachePrepStmts value.
This is an issue, because there is 3 possibles prepare use :

• prepared statement
• Callable statement (stored procedure)
• bulk

This means that even if useServerPrepStmts is disabled, all callable/bulk statement will be cached, possibly reaching max_prepared_stmt_count while useServerPrepStmts is not set. This is an bug, goal is to have the same cache behavior in 3.x than the existing one in 2.x