Support custom mapping for fields and column of arbitrary types.

Motivation.

A user may want to operate with user objects, which types may differ from or incompatible with a column type.
As a special case, a user may want to transparently serialize an arbitrary object to byte[] (BLOB) column.

Description.

To achieve this we can provide an interface for the converter and allow passing custom converters to a mapper.
The converter acts as an interceptor and transforms a value before writing to/after reading from the column.
Mapper API should be refactored as well to support this.

As a PoC, let's add a test with a converter that performs transparent Java serialization arbitrary object to byte[] column.

Converters and automatic typecasting is out of the scope,
the goal is to create API and infrastructure for further extension, e.g.

• provide a standard converter component for cross-platform serialization (based on MessagePack or on IGNITE-15944 ticket ideas)
• optionally add JSON/BSON format support.
• add simple converters for supported native types, e.g. Integer<-->String, and possibly, support implicit typecasting.
• support unsigned types via implicit typecasting mechanics.