Osi: Implement Has/Get/Set methods for section_t and config_t

* Implement convenience methods so that users don't have to loop
  through them manually

Bug: 143515989
Test: atest --host net_test_osi:ConfigTest
Change-Id: I570a49bec9496409ba60f8223c58c9e642b41c1a
Merged-In: I570a49bec9496409ba60f8223c58c9e642b41c1a
(cherry picked from commit ea96adb18201c603a65b49583281a372a830af69)