Add tests with UoM conversion

For `PersistenceThresholdFilter` add a test case that fails when
using temperatures in °C and a threshold in Kelvin. The threshold
should ignore the offset (0 °C = 273,15 K).

Add another test with length to increase coverage.

Signed-off-by: Christoph Gehrke <cgdev@duck.com>

Author: ea21fd6

bundles/org.openhab.core.persistence/src/test/java/org/openhab/core/persistence/filter/PersistenceThresholdFilterTest.java

@@ -102,6 +102,10 @@ private static Stream<Arguments> argumentProvider() {
                 // quantity type, below threshold, absolute, with unit
                 Arguments.of(new QuantityType<>("10 m"), new QuantityType<>("10.002 m"), "mm", false, false),
                 // quantity type, above threshold, absolute, with unit
+                Arguments.of(new QuantityType<>("1 ft"), new QuantityType<>("11 in"), "mm", false, true),
+                // quantity type, below threshold, absolute, with unit
+                Arguments.of(new QuantityType<>("0 °C"), new QuantityType<>("0 °C"), "K", false, false),
+                // quantity type, above threshold, absolute, with unit
                 Arguments.of(new QuantityType<>("-10 °C"), new QuantityType<>("5 °C"), "K", false, true));
     }