wayland: Prioritize the pointer capability to get the current surface

Some mice, especially gaming mice, are able to send keyboard keys and therefore have both CLUTTER_INPUT_CAPABILITY_POINTER and CLUTTER_INPUT_CAPABILITY_KEYBOARD capabilities.

When using one of those mice to select a surface, the keyboard capability takes precedence over the pointer capability resulting in bugs.
For example, pop-up menus can not be closed by clicking in another window.

Prioritize the pointer capability to solve these issues.

Fixes: 80ed79a0 ("wayland: Add default event interface handling seat events")
Closes: #3414

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Please see my comment in the libinput bug report to reproduce the issue.

cc @carlosg