Add unit tests to CI

[Megamouse]

• Adds gtest unit tests to the CI

No idea if this is gonna work...

[kd-11]

Good to see others interested in this. I normally use some headers wrapping EXPECT_EQ, ASSERT_EQ etc locally for testing complicated sections like blit engine (sometimes I accidentally push commits and have to delete them in followup). We do need an official UT integration with CI. ~~Maybe we should AI-generate a base suite?~~