(fixes #3464) Replace assert() usages with assertThat()

[u7683345]

Uses of the assert() function in Kotlin are inherited from Java and are only enabled in the JVM with the -ea flag (enable assertions). Since the -ea flag has "not been enabled and won't be", these current assert() assertions don't do anything.

To fix this the assertThat() assertion is always active, regardless of JVM settings, so this would be more suitable.

Fixes #3463

What changes did you make and why?

• Replaced all occurrences of the assert() function to equivalent assertThat() function calls, in 3 relevant files.
• Imported 3 functions from the hamcrest.CoreMatchers library, assetThat() , equalTo(), and not(), in these files for translating the current assertions over to the hamcrest syntax.

Tests performed

Tested ProdDebug on Pixel 9 with API level 34.

[u7683345]

@nicolas-raoul would you be able to review this? :-)

[nicolas-raoul]

Thanks!

Now I guess we have to find out why this test is failing:

fr.free.nrw.commons.location.LatLngTest > testConstructorBigLongitude FAILED
    java.lang.AssertionError at LatLngTest.kt:26
    
1542 tests completed, 1 failed, 40 skipped

[nicolas-raoul]

Tests pass, thanks! :-)