Added unit tests for `PImage` in `processing:core` #145

Job	Run time
Test Processing	1m 6s
(linux/aarch64) Create Processing Build	8m 22s
(linux/x64) Create Processing Build	7m 46s
(windows/x64) Create Processing Build	15m 30s
(macos/x64) Create Processing Build	5m 24s
(macos/aarch64) Create Processing Build	2m 40s
	40m 48s

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