Add TestValue_Raw

[gavv]

Add new test TestValue_Raw for Value.Raw() method.

It should be similar to other _Raw tests, like TestObject_Raw and TestArray_Raw. But unlike them, it should cover multiple data types, supported by Value. The full list can be borrowed from TestValue_Getters.

Ideally it should be table-driven test.

[Reajang]

Hello! Here is the PR for adding a new test #464