As a part of internal core libraries cleanup move usages of
IoUtils#deleteContents from CorePlatformApi set to framework.
Bug: 154796679
Test: m update-api
Change-Id: If7037029026b6753ab64be09aa52c40e04d5c7b1
Move the tests together with packages/Connectivity code, so both can be
moved to packages/modules/Connectivity together.
Also reorganize unit tests in a unit/ directory, as other tests
(integration/, common/ etc.) have been added in tests/net since they
were created. This makes the directory structure consistent.
Test: atest FrameworksNetTests
Bug: 187814163
Merged-In: I254ffd1c08ec058d594b4ea55cbae5505f8497cc
Change-Id: I254ffd1c08ec058d594b4ea55cbae5505f8497cc
