[mono][aot] Prefer concrete instances instead of gshared ones for met… (#78182)

[mono][aot] Prefer concrete instances instead of gshared ones for met… (#78182)

* [mono][aot] Prefer concrete instances instead of gshared ones for methods containing type equality checks.

For example, calls to Vector<T>.IsSupported cannot be optimized away in a method where T
is T_BYTE because its written as:

```
            get => (typeof(T) == typeof(byte)) ||
                   (typeof(T) == typeof(double)) ||
```

and T_BYTE could be instantiated with an enum whose basetype is byte.

Fixes some of the issues in https://github.com/dotnet/runtime/issues/78163.

* Avoid an assert when compiling Vector<object> instances.