This laxes the check on numerical spans to allow them be specified as whole numbers. So far it was required that they be provided as a double.
This also expands the tests for date ranges to include string types.
Resolves#109340, resolves#104646, resolves#105375.
This adds the documentation for BUCKET as a grouping function and the
addition of the "direct" invocation mode providing a span (in addition
to the auto mode).
