Removed all uses and implementations of set_vector() function across ERC32,
LEON2, and LEON3 BSPs. Replaced with rtems_interrupt_handler_install() and
rtems_interrupt_entry_install().
- Added ERC32_Clear_and_unmask_interrupt() and LEON_Clear_and_unmask_interrupt()
for unmasking logic previously in set_vector().
- Deleted set_vector() definitions and implementations in each BSP.
- Updated related obj.yml files.
- Replaced set_vector() with rtems_interrupt_catch() in shared/gnatcommon.c.
