[SPARK-23046][ML][SPARKR] Have RFormula include VectorSizeHint in pipeline

## What changes were proposed in this pull request?

Including VectorSizeHint in RFormula piplelines will allow them to be applied to streaming dataframes.

## How was this patch tested?

Unit tests.

Author: Bago Amirbekian <bago@databricks.com>

Closes #20238 from MrBago/rFormulaVectorSize.

(cherry picked from commit 186bf8fb)
Signed-off-by: Joseph K. Bradley <joseph@databricks.com>