[C++][Arrow Flight SQL ODBC] Refactor unnecessary nesting in include folders

[alinaliBQ]

Describe the enhancement requested

For context, see this comment. There's many unneeded nesting inside the Arrow Flight SQL ODBC driver, such as odbc/odbcabstraction/include/odbcabstraction. We should refactor to remove the nesting. For example, headers in odbc/odbcabstraction/include/odbcabstraction can be moved to odbc/odbcabstraction.

Component(s)

FlightRPC