Conditionally quote env vars

[saurabhkoshatwar]

Resolves #6997

This PR conditionally quotes environment variable values—only wrapping those containing special characters (like parentheses) that could trigger bash errors. Safe values remain unquoted.

[qiuosier]

This fix avoided some errors. However, there is still error with variable containing double quotes.
For example, when the var is a valid JSON string,

var = "{\"a\": \"b\"}"

after quoting, it will become

"{"a": "b"}"

then, in bash

export var="{"a": "b"}"

will export the var as

{a: b}

which is no longer a valid JSON string.

Shall we use shlex.quote() instead?

[saurabhkoshatwar]

@loadams cpu-torch-latest ci stuck, please rerun

[tjruwase]

@saurabhkoshatwar, thanks for the PR. Is it possible to add a unit test here?
https://github.com/deepspeedai/DeepSpeed/blob/master/tests/unit/launcher/test_user_args.py