Fix SAT warnings (#14202)

* Fix SAT warnings

- checkstyle.ModifierOrderCheck
- checkstyle.OneStatementPerLineCheck
- checkstyle.NeedBracesCheck
- PMD.UseStandardCharsets
- PMD.UseCollectionIsEmpty
- PMD.UnusedLocalVariable
- PMD.SimplifyBooleanReturns where reasonable, suppress where
readability is better without change
- PMD.SimplifyBooleanExpressions

* Include StandardCharsets

Signed-off-by: Holger Friedrich <mail@holger-friedrich.de>

bundles/org.openhab.binding.plugwise/src/main/java/org/openhab/binding/plugwise/internal/protocol/field/MACAddress.java

@@ -37,6 +37,7 @@ public class MACAddress {
         return result;
     }
 
+    @SuppressWarnings("PMD.SimplifyBooleanReturns")
     @Override
     public boolean equals(@Nullable Object obj) {
         if (this == obj) {