fix(input): make maxlength and minlength work with non-string values

Request Type: bug

How to reproduce: 

Component(s): misc core

Impact: small

Complexity: small

This issue is related to: 

**Detailed Description:**



**Other Comments:**

Validity for inputs with maxlength attribute and an underlying non-string model value is always false: e.g. the length property for a numeric data type returns undefined