add SELECT.forUpdate(ignoreLocked)

[kulliax]

add the forUpdate(ignoreLocked) property on CQL Select, see cap-js/cds-dbs#917

official sql docs:
https://help.sap.com/docs/SAP_HANA_PLATFORM/4fe29514fd584807ac9f2a04f6754767/20fcf24075191014a89e9dc7b8408b26.html?locale=en-US#loio20fcf24075191014a89e9dc7b8408b26__for_update_clause
https://www.postgresql.org/docs/17/sql-select.html

[johannes-vogel]

Hi @kulliax,

thanks for opening the PR.
Before merging, we first have to discuss whether we want to make that an official API. So far, the tendency was not make it a public API.

[kulliax]

Hi @johannes-vogel ,

I hope the discussion goes well. It would be very helpful to publicly document the functionality that has already been implemented.