The test-conf build_pattern attempted to convert known constant strings
into integer values. However, it did so by always converting the string
value to an integer if possible and then complaining if the key wasn't
of the expected type. This lead to error messages on "style": "Regular"
since "Regular" was recognized as "weight".

Instead, only attempt conversion from string to integer if the key is
the name of an object which can take an integer type. This eliminates
the spurious non-fatal errors reported when parsing
test-90-synthetic.json.

This also fixes an issue where the created value was given the type of
the object found, but the integer field was assigned. Instead, check
that the object type can take an integer and always set the value type
to integer.