FilterExpression doesn't work with LocalDateTime values

When passing in a LocalDateTime, the expression parser needlessly converts into a `Date`

This makes the filter unusable if you want to convert it to JPA format or SQL using `filterExpression.getExpression(ExpressionFormat.JPA);`

Start at FilterExpression.getExpression(ExpressionFormat.JPA) and reproduce the reported behavior with a LocalDateTime value. Trace where the expression parser converts it to Date; done means JPA and SQL output preserve the LocalDateTime value and the existing filter behavior remains intact.

Written by the indexing model from the issue text.