Support using the same numeric-valued metatag twice in the same search.
Numeric-valued metatags are those taking an integer, float, filesize, or
date argument. Previously using the same metatag twice would cause the
second metatag to overwrite the first metatag.
Examples:
* "id:>5 id:<10"
* "width:>500 width:<1000"
* "date:>2019-01-01 date:<2020-01-01"