Use database expressions in DecimationProcessor and the related code. (Currently we are using Expression.java library to obtain column expression values when producing decimation (heatmap) data.

Since we are using database expressions for filtering, we need to make sure the same expressions are used to produce the data.

Ideally, we should be using db for all expression evaluation on the server side and remove all references to Expressions.java. We'll still keep Expression.js on client side for user-friendly column expression validation.

Currently server-side expression library is used in:
DecimationProcessor.java
QueryUtil.java (doDecimation)
IpacTablePartProcessor.java (deprecated getDataFile - decimation)
HistogramProcessor.java (old single-trace charts)
XYGenericProcessor.java (old single-trace charts)