Add UDP encapsulation tests for IpSecService.

This commit adds tests to ensure that IpSecService properly
handles UDP-encapsulation transforms correctly.

Bug: 76110065
Test: Added: testCreateTransportModeTransformWithEncap,
             testCreateTunnelModeTransformWithEncap.
      Command: runtest frameworks-net
      Verified on taimen.
Change-Id: Ie05bc5354266806c2d03b0b3d73a4696a89eccf2