Moves the byte-identical 19-file ExpressionFactory/Query tree (duplicated
across Snowflake and SqlServer) into the new Strata.SqlTools.Query project
under the flat namespace Strata.SqlTools.Query. Both dialect projects now
reference the shared project; the Snowflake copies are deleted.
Also folds in the IDE0028 fix on CalculationFilterGroup.GetValidFilters
(collection expression []), which resolves both new-code IDE0028 smells
in one place now that there is a single copy.
Eliminates the 63 new duplicate lines flagged on the PR and removes the
largest contributor to the project's 11.1% duplication density. No
behavioral change: the moved types are identical to the originals.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
