[gdb] Allow gdb.Value to take a Buffer plus a Type (#16006)

If a type is passed that is not None, it always goes through the
buffer protocol, which interestingly means you can't pass
an existing gdb.Value together with a type. You have to use the
cast method for that purpose.

Author: timo

stubs/gdb/gdb/__init__.pyi

@@ -111,7 +111,12 @@ class Value:
     def __ge__(self, other: _ValueOrNative, /) -> bool: ...
     def __getitem__(self, key: int | str | Field, /) -> Value: ...
     def __call__(self, *args: _ValueOrNative) -> Value: ...
-    def __init__(self, val: _ValueOrNative, type: Type | None = None) -> None: ...
+
+    @overload
+    def __init__(self, val: _ValueOrNative, type: None = None) -> None: ...
+    @overload
+    def __init__(self, val: _BufferType, type: Type) -> None: ...
+
     def cast(self, type: Type) -> Value: ...
     def dereference(self) -> Value: ...
     def referenced_value(self) -> Value: ...