Allow accepting `Object`s in `QuerydslPredicateBuilder` instead of `String` values only

[mp911de]

QuerydslPredicateBuilder should accept a MultiValueMap with Object values to broaden reuse of predicate assembly instead of limiting values to String. Spring GraphQL deserializes values to proper objects (see spring-projects/spring-graphql#311) while the use cases for QuerydslPredicateBuilder originate in Spring WebMVC's request parameters that are represented as strings.