fix(data/odbc): change the preparing of uuid column type so that isNu…

[solarobot]

#5017
use prepareVariableLen instead so that the actual size can be determined by isNull(pos, row) in extractor.

inline void Preparator::prepare(std::size_t pos, const Poco::UUID&)
{
	//use prepareVariableLen instead so that the actual size can be determined by isNull(pos, row) in extractor.
	prepareVariableLen<char>(pos, SQL_C_BINARY, 16, DT_CHAR);
	//prepareCharArray<char, DT_CHAR_ARRAY>(pos, SQL_C_BINARY, 16, 16);
}

[aleks-f]

there should be a unit test for at least one back-end.

we are currently CI-testing Oracle and SQLServer:

poco/.github/workflows/ci.yml

Lines 774 to 787 in 7a23a03

	oracle:
	image: container-registry.oracle.com/database/express:21.3.0-xe
	env:
	ORACLE_PWD: poco
	ports:
	- 1521:1521
	sqlserver:
	image: mcr.microsoft.com/mssql/server:2022-latest
	env:
	MSSQL_PID: Express
	ACCEPT_EULA: Y
	MSSQL_SA_PASSWORD: Pocopoco1
	ports:
	- 1433:1433

[solarobot]

the existing unit test should be ok since there is no new logic added.