No union type and virtual methods support in ArkTS analyzer

[MaxMilshin]

For this sample, at line 32, analyzer can't resolve method isSame because variable c have union type (Foo|Bar), which is currently not supported.

Even if we were to support union types, there remains a broader issue: weak support for virtual methods in the IFDS core and specifically in the ArkTS extension. Currently, every call statement has a single callee method, which is not virtual. This limitation prevents running analyses like this one.

P.s. that issue related to lipen/taint-panda branch.