[Wasm][KeyPath] Resolve absolute function pointer as identity

[kateinoigakukun]

Emit and resolve idValue of KeyPath as an absolute pointer if relative
function pointer is turned-off on Wasm target.
The existing ABI can't distinguish an idValue between function pointer
or data pointer in use-site at compile-time and also at runtime. So this
patch adds a new id resolution scheme ResolvedAbsolute to distinguish
them at runtime properly.

[kateinoigakukun]

@swift-ci Please test

[kateinoigakukun]

@swift-ci Please test

[kateinoigakukun]

@jckarter Could you take a look when you have time?

[jckarter]

I don't think we need to introduce a new runtime representation, since the absolute and relative representations should be mutually exclusive for any one runtime platform. It would be better to conditionalize the interpretation based on whether the platform uses absolute or relative references.

[kateinoigakukun]

@jckarter

since the absolute and relative representations should be mutually exclusive for any one runtime platform

ResolvedAbsolute and relative Resolved are not mutually exclusive at runtime because both resolution schemes are used on Wasm. Pointers to data section (for ComputedPropertyId::DeclRef) are relative, and pointers to function (for ComputedPropertyId::Function) are absolute on Wasm.

[jckarter]

I see. In that case, this looks OK.

[kateinoigakukun]

@swift-ci Please test and merge