When constructing a value fetcher, the 'parsesArrayValue' flag must match
`FieldMapper#parsesArrayValue`. However there is nothing in code or tests to
help enforce this.
This PR reworks the value fetcher constructors so that `parsesArrayValue` is
'false' by default. Just as for `FieldMapper#parsesArrayValue`, field types must
explicitly set it to true and ensure the behavior is covered by tests.
Follow-up to #62974.