[backport][bugfix] Fixes #16852 by adding click_x and click_y variables to resolve actions

[pblottiere]

Description

Layer actions triggered by identify + right click don't have click_x and click_y variables populated (see https://issues.qgis.org/issues/16852).

Some tests have been added.

This PR supersedes #5068.

Backport of #5597.

Checklist

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• New unit tests have been added for core changes
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