[C++][Flight SQL ODBC] Move class definitions to a `type_fwd.h` file

[alinaliBQ]

Describe the enhancement requested

AC:
Create type_fwd.h for the following classes:

• Statement

• ResultSet

• ResultSetMetadata

• ODBCEnvironment

• ODBCDescriptor

• ODBCStatement

• ODBCConnection

Remove class definitions for these classes from existing files

Parent issue: #30622

Component(s)

FlightRPC, C++

[lidavidm]

Issue resolved by pull request 48596
#48596