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.digitalstrom/src/main/java/org/openhab/binding/digitalstrom/internal/lib/climate/datatypes/AssignSensorType.java

@@ -83,6 +83,7 @@ public class AssignSensorType {
      * 
      * @see java.lang.Object#equals(java.lang.Object)
      */
+    @SuppressWarnings("PMD.SimplifyBooleanReturns")
     @Override
     public boolean equals(Object obj) {
         if (this == obj) {

bundles/org.openhab.binding.digitalstrom/src/main/java/org/openhab/binding/digitalstrom/internal/lib/structure/devices/deviceparameters/impl/DeviceSensorValue.java

@@ -267,6 +267,7 @@ public class DeviceSensorValue {
      *
      * @see java.lang.Object#equals(java.lang.Object)
      */
+    @SuppressWarnings("PMD.SimplifyBooleanReturns")
     @Override
     public boolean equals(Object obj) {
         if (this == obj) {