Move from JCP to Jakarta

[struberg]

The spec leads @Emily-Jiang and @struberg decided to withdraw this specification from the JCP and continue the work under the JakartaEE umbrella.

This means we will rename all packages to jakarta.* etc.

[Daniel-Dos]

very good : )

[teobais]

Shall we add a good first issue label to this one? :-)
It would be a really good start for beginners, I guess.