Move VPN related platform code unit tests

As VpnProfile, VpnManager and Ik2v2VpnProfile are platform codes,
their unit tests should be better to be placed together with
their source code.

Move the unit test from module to platform for better test
configuration.

Test: atest FrameworksNetTests FrameworksVpnTests
Change-Id: Idb5033e23306b714a29d953866ca5a5771fb78a7
3 files changed