API change to 3.0.91: improve memory management of raw SQL execution and preparing

Summary:

• Change KDbSqlResult* KDbConnection::executeSQL to QSharedPointer<KDbSqlResult> KDbConnection::prepareSql (fixes risks of memory leaks and unfinished execution when resulting object is ignored)
• Change bool KDbConnection::executeVoidSQL to bool KDbConnection::executeSql (also in Kexi)
• Change KDbConnection::insertRecord to return QSharedPointer<KDbSqlResult> (fixes risks of memory leaks and unfinished execution when resulting object is ignored)
• Change KDbConnection::recentSQLString() to recentSqlString()
• Change KDbSqlRecord* KDbSqlResult::fetchRecord() to QSharedPointer<KDbSqlRecord> fetchRecord()
• Change KDbSqlResult* KDbPreparedStatementInterface::execute() to QSharedPointer<KDbSqlResult> KDbPreparedStatementInterface::execute()
• Change KDb::lastInsertedAutoIncValue(KDbSqlResult *result, ...) to KDb::lastInsertedAutoIncValue(QSharedPointer<KDbSqlResult>, ...)
• Update drivers accordingly
• KDb & Kexi: Replace KDbConnection::executeVoidSQL uses with KDbConnection::executeSql and Replace KDbConnection::executeSQL uses with KDbConnection::prepareSql where needed (fix memory leak and unfinished execution)

Test Plan: Run all autotests of KDb, build and try Kexi with sqlite/pgsql/mysql projects.

Reviewers: piggz

Subscribers: anthonyfieroni

Tags: KDb

Maniphest Tasks: T5992

Differential Revision: https://phabricator.kde.org/D5771