Don't globally disable any ShellCheck warnings (#55165)
Summary:
https://github.com/pytorch/pytorch/issues/47786 updated ShellCheck and fixed the warnings that it was already giving in CI (since it previously didn't cause the job to fail). https://github.com/pytorch/pytorch/issues/54069 enabled two ShellCheck warnings that previously were globally disabled. This PR continues the trend by reenabling the remaining four ShellCheck warnings that previously were globally disabled.
Also, this PR puts as many remaining ShellCheck arguments as possible into `.shellcheckrc` to make it easier to integrate with editors. For instance, in VS Code, this is now all that is needed (due to https://github.com/koalaman/shellcheck/issues/1818 and the fact that VS Code only runs ShellCheck on one file at a time):
```json
{
"shellcheck.customArgs": [
"--external-sources"
]
}
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55165
Test Plan:
[The "Lint / quick-checks" job in GitHub Actions](https://github.com/pytorch/pytorch/pull/55165/checks?check_run_id=2250098330), or this command if you want to check locally:
```
.jenkins/run-shellcheck.sh
```
Reviewed By: walterddr
Differential Revision: D27514119
Pulled By: samestep
fbshipit-source-id: f00744b2cb90a2ab9aa05957bff32852485a351f
