ServletAttributesMap inherited default implementations of the size
and isEmpty methods from AbstractMap which delegates to the Set returned
by entrySet. ServletAttributesMap's entrySet method made this fairly
expensive, since it would copy the attributes to a List, then use a
Stream to build the Set. To avoid the cost, add implementations of
isEmpty / size that don't need to call entrySet at all.
Additionally, change entrySet to return a Set view that simply lazily
delegates to the underlying servlet request for iteration.
Closes gh-32189
Patrick Strawderman
0fdf759896