[BUG] upper_bound and lower_bound functions incorrect results when searching GDF_STRING_CATEGORY values

[jeanp413]

Describe the bug
upper_bound and lower_bound functions give incorrect results when searching GDF_STRING_CATEGORY values

This is caused because the column's categories are not synced before doing the search

Steps/Code to reproduce bug
Call upper_bound / lower_bound with the cudf::table table and cudf::table values parameters containing a columns whose types are GDF_STRING_CATEGORY

Expected behavior
upper_bound and lower_bound should give correct results when searching GDF_STRING_CATEGORY values

[kuhushukla]

Based on some java side tests GDF_STRING also seems to be broken for lower/upper bound.

[harrism]

This is fixed in the libcudf++ API by #3229

@kuhushukla @jeanp413 please reopen if you find this is not the case.