Add @type_check_only to stub-only private classes in various third-party stubs (#15535)

stubs/fpdf2/fpdf/_fonttools_shims.pyi

@@ -2,10 +2,11 @@
 from abc import ABCMeta, abstractmethod
 from collections.abc import Mapping
 from logging import Logger
-from typing import Any, Protocol
+from typing import Any, Protocol, type_check_only
 from typing_extensions import TypeAlias
 
 # from fonttools.ttLib.ttGlyphSet
+@type_check_only
 class _TTGlyph(Protocol):
     def __init__(self, glyphSet: _TTGlyphSet, glyphName: str) -> None: ...
     def draw(self, pen) -> None: ...

stubs/fpdf2/fpdf/drawing.pyi

@@ -59,7 +59,7 @@ class GraphicsStateDictRegistry(OrderedDict[Raw, Name]):
 
 def number_to_str(number: Number) -> str: ...
 def render_pdf_primitive(primitive: _Primitive) -> Raw: ...
-
+@type_check_only
 class _DeviceRGBBase(NamedTuple):
     r: Number
     g: Number
@@ -75,6 +75,7 @@ class DeviceRGB(_DeviceRGBBase):
     def colors255(self) -> tuple[Number, Number, Number]: ...
     def serialize(self) -> str: ...
 
+@type_check_only
 class _DeviceGrayBase(NamedTuple):
     g: Number
     a: Number | None
@@ -88,6 +89,7 @@ class DeviceGray(_DeviceGrayBase):
     def colors255(self) -> tuple[Number, Number, Number]: ...
     def serialize(self) -> str: ...
 
+@type_check_only
 class _DeviceCMYKBase(NamedTuple):
     c: Number
     m: Number