1. Introduced CPU Exception Handler Library to provide the CPU exception handlers...

1. Introduced CPU Exception Handler Library to provide the CPU exception handlers and add one NULL library instance.
2. Updated DXE Core, BootScriptExecutorDxe and CapsuleX64Pei to consume CPU Exception Library to setup the default CPU Exception handlers.

Signed-off-by: vanjeff
Reviewed-by: jyao1
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@13097 6f19259b-4bc3-4df7-8a09-765794883524