Consider the following code:
```
fun test(a: List<String>) {
a.first()
}
```
The dispatch receiver type of `first` in this case is `List<T>` before
this change. After this change, it's `List<String>`.
In addition, this change also replace the dispatch receiver type with
the more specific type if available. For example, consider the following
```
class MyList: ArrayList<String>()
fun test(a: MyList) {
a.get(0)
}
```
The dispatch receiver type of `get` is `MyList`, instead of
`ArrayList<String>`. That is, a fake override is created in this case.
Descriptors are already supposed to be sorted in scopes. The problem is
that rendering descriptors for sorting takes a lot of time (~1.5% of
total compilation time of intellij with JVM IR), and simple heuristics,
like comparing by names first, don't fully help with it.
#KT-48233
Before this commit, FIR mangler effectively dropped f/o parameter with
invisible type from this module. It could lead to signature clashes.
Now we insert classId in mangler string instead.
This fixes FIR bootstrap.
Before this commit we initialized delegate fields in primary constructor,
that could provoke NPE in case delegate is used in initializer of
some property backing field.
Now we initialize delegate fields directly instead.
Tianyu Geng