Max and min aggs were producing wrong results for unsigned_long field
if field was indexed. If field is indexed for max/min aggs instead of
field data, we use values from indexed Points, values of which
are derived using method pointReaderIfPossible. Before
UnsignedLongFieldType#pointReaderIfPossible was incorrectly
producing values, as it failed to shift them back to original
values.
This patch fixes method pointReaderIfPossible to produce
correct original values.
Relates to #60050
1287df4074