Move _ISR_Handler() to a separate file since it is now only used if a handler
is installed by _CPU_ISR_install_raw_handler().
Statically initialize the traps for external interrupts to use the new
_SPARC_Interrupt_trap() which directly dispatches the interrupt handlers
installed by rtems_interrupt_handler_install() via the BSP-provided
_SPARC_Interrupt_dispatch().
Since the trap table is now fully statically initialized, there is no longer a
dependency on the Cache Manager in the default configuration.
Update #4458.
