fix(ivy): identify all ESM5 decorated classes - #27848

In ESM5 decorated classes can be indicated by calls to `__decorate()`.
Previously the `ReflectionHost.findDecoratedClasses()` call would identify
helper calls of the form:

```
SomeClass = tslib_1.__decorate(...);
```

But it was missing calls of the form:

```
SomeClass = SomeClass_1 = tslib_1.__decorate(...);
```

This form is common in `@NgModule()` decorations, where the class
being decorated is referenced inside the decorator or another
member.

This commit now ensures that a chain of assignments, of any length,
is now identified as a class decoration if it results in a call to
`__decorate()`.

Fixes angular#27841