ArmPkg/ArmExceptionLib: fold exception handler prologue into vector table

ArmPkg/ArmExceptionLib: fold exception handler prologue into vector table

Unlike the AArch32 vector table, which has room for a single instruction
for each exception type, the AArch64 exception table has 128 byte slots,
which can easily hold the shared prologues that are emitted out of line.

So refactor this code into a single macro, and expand it into each vector
table slot. Since the address of the command handler entry point is no
longer patched in by the C code, we can just emit the literal into each
vector entry directly.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Eugene Cohen <eugene@hp.com>