Reworked AbstractPlatform::get*Expression() methods

Modified AbstractPlatform::getLocateExpression() and ::getSubstringExpression() signatures

Changed the type of $char in AbstractPlatform::getTrimExpression()`from string|false to ?string

Connection::quote() can only quote strings

Changed the type of `$char` in `AbstractPlatform::getTrimExpression()` from `string|false` to `?string`

1. The argument is always available since the method is only called from listTableIndexes() which requires a table name.
2. The argument itself seems a workaround and only needed to bypass the fact that the SQLiteSchemaManager violates the method contract: instead of reformatting the provided data it fetches more data from the DB schema which requires a table name. This argument should be dropped completely later.

Converted Connection and Statement methods which returned false in case of a failure into void

Moved rowCount() from Statement to ResultStatement

Transaction-related Statement methods return void

Statement::fetchColumn() will throw an exception in the case of invalid index

Made the OFFSET in LIMIT queries non-nullable integer defaulting to 0

Removed dbal:import CLI command

Fixed and suppressed issues found by PHPStan on develop

Removed support for DB-generated UUIDs

Revert complex type specification in Connection

Added "string" mapping in SqlitePlatform

  - fix 'Unknown database type string requested, Doctrine\DBAL\Platforms\SqlitePlatform may not support it.' error