PDI-10869: Fix various issues with timestamp support (Constant, Rowgenerator, Calculator) and apply checkstyle.

Conflicts:

	core/src/org/pentaho/di/core/row/ValueDataUtil.java
	core/src/org/pentaho/di/core/row/ValueMetaInterface.java
	core/src/org/pentaho/di/core/row/value/ValueMetaTimestamp.java
	engine/src/org/pentaho/di/trans/steps/calculator/Calculator.java
	engine/src/org/pentaho/di/trans/steps/calculator/CalculatorMeta.java
	engine/src/org/pentaho/di/trans/steps/constant/Constant.java
	engine/src/org/pentaho/di/trans/steps/rowgenerator/RowGenerator.java
	test/org/pentaho/di/trans/steps/constant/ConstantTest.java
	test/org/pentaho/di/trans/steps/rowgenerator/RowGeneratorTest.java
	test/org/pentaho/di/trans/steps/sort/SortRowsTest.java