RFR: 8344112: Remove code to support security manager execution mode from DatagramChannel implementation

[Daniel Fuchs]

On Wed, 13 Nov 2024 14:07:44 GMT, Alan Bateman <alanb at openjdk.org> wrote:

> Remove code required for the now defunct SecurityManager execution mode from DatagramChannelImpl. Dropping this execution mode means that untrustedReceive can be removed. Additionally, blockingReceive (used to support the adaptor) no longer needs a loop to drop datagrams that the SecurityManager rejects.
> 
> Once this change is in then it allow reverting some changes introduced to avoid pinning in the adaptor's receive method, a consequence of have both JEP 486 and JEP 491 integrated.

Marked as reviewed by dfuchs (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk/pull/22072#pullrequestreview-2433564804