[nightcolor] Print a debug message upon receiving new location from kded module

Summary:
This can be useful for debugging whether Night Color manager actually
receives new location data from colorcorrectlocationupdater kded module.

CCBUG: 412211

Test Plan:
Run kwin with QT_LOGGING_RULES="kwin_colorcorrection.debug=true"

Run from the terminal the following two commands
    qdbus org.kde.kded5 /kded unloadModule colorcorrectlocationupdater
    qdbus org.kde.kded5 /kded loadModule colorcorrectlocationupdater

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D24236