ELD is crashing when AArch64 objects contain unsupported relocations

[nezetic]

Due to a missing assert, eld crashes when trying to link AArch64 objects including unsupported relocations.

This is due to pType not being validated before accessing ApplyFunctions in AArch64Relocator::getSize.

Relocator::Size AArch64Relocator::getSize(Relocation::Type pType) const {
   return ApplyFunctions[pType].size;
 }

#772 is adding the missing assert along with additional checks and tests.