Drop cudo backend (#4018)

Author: r4victor

src/dstack/_internal/core/backends/configurators.py

@@ -44,15 +44,6 @@
 except ImportError:
     pass
 
-try:
-    from dstack._internal.core.backends.cudo.configurator import (
-        CudoConfigurator,
-    )
-
-    _CONFIGURATOR_CLASSES.append(CudoConfigurator)
-except ImportError:
-    pass
-
 try:
     from dstack._internal.core.backends.datacrunch.configurator import (
         DataCrunchConfigurator,

src/dstack/_internal/core/backends/cudo/__init__.py

@@ -4,6 +4,8 @@
 
 from dstack._internal.core.models.common import CoreModel
 
+# TODO: Cudo is deprecated and will be removed in the future
+
 
 class CudoAPIKeyCreds(CoreModel):
     type: Annotated[Literal["api_key"], Field(description="The type of credentials")] = "api_key"