Support for always true or false predicates in filters

Feature request:
Add support for always true or false in filters. This will facilitate autogenerated queries by other bi tools to work.
Some examples:
This may be the query generated (even though the `TRUE` can be elided, it may be autogenerated by a tool):
```
SELECT * FROM table WHERE (TRUE) AND (a = 3)
```
support for 1=0 or 1=1 (some bi tools use this form to generate predicates):
```
SELECT * FROM table WHERE (1 = 0)
```

The issue names no files, tests, or entry points. Start by locating the SQL filter parsing and planning paths for the provided TRUE, FALSE, 1 = 0, and 1 = 1 examples; done means these predicates work in autogenerated filter queries without breaking the existing a = 3 case.

Written by the indexing model from the issue text.