Build: Configuration for Regression IPC test

- Disable Regression in ConfigCoreIPC.cmake and
  ConfigCoreIPCTfmLevel2.cmake.
- Add new build configuration to run regresstion with IPC model and IPC
  model isolation level 2.
- Add explicit setting for basic project build variables in all build
  configurations

Change-Id: I9a627ca08209a5b8e295c3cac9538d6e80f2e669
Signed-off-by: Edison Ai <edison.ai@arm.com>