[ConstExpr] Relax expectations in ArrayAppendElement to allow direct-passed element

[kubamracek]

When using arrays in a constant-folding string interpolation, under Embedded Swift, we can hit an assert:

Assertion failed: (getKind() == Address), function getAddressValue, file SILConstants.cpp, line 674.
...
7  swift-frontend           0x00000001062bd580 swift::SymbolicValue::getAddressValue(llvm::SmallVectorImpl<unsigned int>&) const (.cold.2) + 0
8  swift-frontend           0x00000001012eb390 swift::SymbolicValue::getAddressValue(llvm::SmallVectorImpl<unsigned int>&) const + 136
9  swift-frontend           0x0000000101021678 swift::ConstExprFunctionState::loadAddrValue(swift::SILValue, swift::SymbolicValue) + 88
10 swift-frontend           0x000000010101ea04 swift::ConstExprFunctionState::computeWellKnownCallResult(swift::ApplyInst*, WellKnownFunction) + 2732

This PR fixes that by relaxing the expectation inside the handling of WellKnownFunction::ArrayAppendElement, which have only been expecting that Array.append is generic (non-specialized) and takes the element parameter indirectly. That's not always true under Embedded Swift where Array.append is going to be specialized.

rdar://139351327

[kubamracek]

@swift-ci please test

[kubamracek]

@swift-ci please built toolchain macOS platform

[kubamracek]

@swift-ci please build toolchain macOS platform

[kubamracek]

@swift-ci please test

[kubamracek]

@swift-ci please build toolchain macOS platform

[kubamracek]

@swift-ci please test

[kubamracek]

@swift-ci please build toolchain macOS platform