Move Ethernet related files to f/b/packages/ConnectivityT.

ethernet-service is going to be moved into Connectivity mainline module.
Notice that below sources are also only used in the ethernet framework
during compiling the filegroup: framework-connectivity-ethernet-sources.
Move them from f/b to f/b/packages/ConnectivityT as well.

Ethernet framework only related files:
    - IInternalNetworkManagementListener.aidl
    - InternalNetworkManagementException.java
    - InternalNetworkManagementException.aidl
    - InternalNetworkUpdateRequest.java
    - InternalNetworkUpdateRequest.aidl

Ethernet service only related files:
    - DelayedDiskWrite.java(IpConfigStore imports this class)

Bug: 210586283
Test: build pass
      atest FrameworksNetTests
      atest EthernetServiceTests
Change-Id: I1ec2d1d182c04f3f2acc9b757d5061ca749a4a3c