[Thread] support customize meshcop txt via resourceoverlay

Currently support customizing the vendor name, vendor oui and model
name.

Bug: 311324956
Test: atest ThreadNetworkIntegrationTests:android.net.thread.ServiceDiscoveryTest#meshcopOverlay_vendorAndModelNameAreSetToOverlayValue
Change-Id: I3ad916112c73c3f8a7eef4e3fa8d421ab9bf8276
3 files changed