Fix coregistration button positions

[Hafsa-shoaib989]

This PR fixes issue #790, which involves the incorrect positioning of the fiducial buttons for the Left Ear and Right Ear in the coregistration Image and Patient tabs. Previously, the buttons were incorrectly placed, with the Left Ear button on the right side and the Right Ear button on the left side. This update switches their positions to correctly match the top-down view of the head.

Changes Made:
Updated the positions of the buttons in the constants.py file for both tabs.
Updated the labels in the marker.py file.

Testing:
Verified that the Left Ear and Right Ear buttons are now correctly positioned in the Image tab.
Verified that the Left Ear and Right Ear buttons are now correctly positioned in the Patient tab.

Hi @henrikkauppi @vhosouza @tfmoraes please review this new PR.

[Rakhesis]

Problems:

• In Object Registration, Left and Right vtkActors are mixed up, since their indexes are hardcoded.

Possibly unintentional:

• Changes fiducial registration order from "Left->Nasion->Right" to "Right->Nasion->Left"

Other:
Is there a reason why existing constants are swapped around here, instead of swapping the positions of the "Left" and "Right" buttons in the sizers? Something like this:
MOD__Swap_left_and_right_in_fiducial_registration.patch

[henrikkauppi]

Hi, there is no need to make changes to the object fiducials or object registration as those are separate from the image and tracker fiducials. As mentioned by @Rakhesis it would probably be easier to switch the positions of the left and right buttons when adding them to sizers in task_navigator.py rather than changing the constants.