SIL function can be serialized with different kinds: [serialized] or

[serialized_for_package] if Package CMO is enabled. The latter kind
allows a function to be serialized even if it contains loadable types,
if Package CMO is enabled. Renamed IsSerialized_t as SerializedKind_t.

The tri-state serialization kind requires validating inlinability
depending on the serialization kinds of callee vs caller; e.g. if the
callee is [serialized_for_package], the caller must be _not_ [serialized].
Renamed `hasValidLinkageForFragileInline` as `canBeInlinedIntoCaller`
that takes in its caller's SerializedKind as an argument. Another argument
`assumeFragileCaller` is also added to ensure that the calle sites of
this function know the caller is serialized unless it's called for SIL
inlining optimization passes.

The [serialized_for_package] attribute is allowed for SIL function, global var,
v-table, and witness-table.

Resolves rdar://128406520

lib/SIL/IR/SILModule.cpp

@@ -936,7 +936,7 @@ void SILModule::performOnceForPrespecializedImportedExtensions(
 }
 
 SILProperty *
-SILProperty::create(SILModule &M, bool Serialized, AbstractStorageDecl *Decl,
+SILProperty::create(SILModule &M, unsigned Serialized, AbstractStorageDecl *Decl,
                     std::optional<KeyPathPatternComponent> Component) {
   auto prop = new (M) SILProperty(Serialized, Decl, Component);
   M.properties.push_back(prop);