Summary:
This is a second attempt at pytorch#51214. It should achieve the same goals with (as far as I can tell) no disadvantages, but the advantages are a bit less pronounced than in the more dictatorial approach that pytorch#51214 took:

- Unfortunately, I was unable to figure out how to include [the `mypy` configuration given in the docstring of `tools.mypy_wrapper.main`](https://github.com/pytorch/pytorch/blob/7115a4b8707115b81417481fb6240617ae934806/tools/mypy_wrapper.py#L81-L89), because as walterddr pointed out, `"${env:HOME}/miniconda3/envs/pytorch/bin/python"` is not guaranteed to be correct on everyone's machine:
  ```json
  {
    "python.linting.enabled": true,
    "python.linting.mypyEnabled": true,
    "python.linting.mypyPath": "${env:HOME}/miniconda3/envs/pytorch/bin/python",
    "python.linting.mypyArgs": [
      "${workspaceFolder}/tools/mypy_wrapper.py"
    ]
  }
  ```

  Importantly, this does not work:
  ```json
  "python.linting.mypyPath": "${workspaceFolder}/tools/mypy_wrapper.py"
  ```
  This is because VS Code does not run the given `mypy` command inside of the user's specified virtual environment, so for instance, on my system, setting the `mypy` command to directly call `tools/mypy_wrapper.py` results in using `mypy 0.782` instead of the correct `mypy 0.812`.

  Sadly, [this](https://code.visualstudio.com/docs/editor/variables-reference#_configuration-variables) does not work either, although I'm not sure why:
  ```json
  {
    "python.linting.mypyPath": "${config:python.pythonPath}",
    "python.linting.mypyArgs": [
      "${workspaceFolder}/tools/mypy_wrapper.py"
    ]
  }
  ```

- As a result, `git clean -fdx; tools/vscode_settings.py` still results in some loss of useful configuration.

One other thing to note: as `.vscode/settings_recommended.json` shows, there are some configuration sections that only take effect within the context of a `"[language]"`, so currently, if a dev already has one of those settings, it would be entirely overwritten by `tools/vscode_settings.py` rather than a graceful merge. This could probably be fixed by using a deep merge instead of the current shallow merge strategy.

Pull Request resolved: pytorch#57671

Test Plan:
If you want, you can typecheck the small script added by this PR (no output is expected):
```sh
tools/mypy_wrapper.py $PWD/tools/vscode_settings.py
```
You can also try running it to update your own VS Code workspace settings:
```sh
tools/vscode_settings.py
```
This should have minimal impact on your existing `tools/settings.json` file other than enabling the few explicitly recommended settings (e.g. it should not reorder or remove any of your existing settings).

Reviewed By: malfet

Differential Revision: D28230390

Pulled By: samestep

fbshipit-source-id: 53a7907229e5807c77531cae4f9ab9d469fd7684