] Auto-generate stubs for named_resources (attempt2) (#1161)

Summary:


Internal
Generate stubs for all the methods generated by the decorator of `named_resources`.

Previous attempt reverted D83985902 because of autodeps issues. 
Genrule that looks at the all the named_resources and generates a file `named_resources.pyi` which is used by the test. 


Three targets added
1. `//torchx/fb/stubgen:generate_named_resources_stub`
2. `//torchx/specs:named_resources_stubs`
3.  //torchx/specs:lib_core_srcs with srcs and deps common between newly created ones and  //torchx/specs:lib_core. 

Some autodeps related quirks. [See post and comments here](https://fb.workplace.com/groups/556728033594708/posts/858891180045057/?comment_id=861391636461678&reply_comment_id=861443023123206). 
1. Add noautodeps labels to the `//torchx/specs:lib_core_srcs` so its not added everywhere and triggers a cascade of changes. 
2. Add  the following to `import_prefix_map.toml` so `//torchx/specs:lib_core` is imported as needed. 
```
"torchx.specs.fb" = "//torchx/specs:lib_core"
"torchx.specs.api" = "//torchx/specs:lib_core"
"torchx.specs.builders" = "//torchx/specs:lib_core"
``` 

Additionally,
Modify some named resources as well.
Fix some imports for completion

Reviewed By: kiukchung

Differential Revision: D86111386

Author: AbishekS

torchx/specs/test/named_resources_test.py

@@ -8,7 +8,6 @@
 # pyre-strict
 
 
-import os
 import unittest
 from unittest.mock import MagicMock, patch