zephyr: Update to 3.4.0

Use a commit ahead of the v3.4.0 tag in order to capture some crucial
bug fixes introduced after the release.

Reflect the change in the documentation.

Update the target cyclonedds commit accordingly.

Issue-Id: SCM-6574
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
Change-Id: I332658fe22043ddc821475c557f6ac188e83ee9d