[master] Convert stdin string to bytes regardless of stdin_raw_newlines

[niklasr22]

What does this PR do?

What issues does this PR fix or reference?

Fixes issue #62501

Previous Behavior

The following error was thrown when running cmd.run with a str passed via stdin and stdin_raw_newlines=True

Passed invalid arguments to cmd.run: memoryview: a bytes-like object is required, not 'str'

New Behavior

String also gets converted to bytes when stdin_raw_newlines=True, so no error is thrown

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes

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PR Guidelines.

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[niklasr22]

Maybe the fix is also interesting for the 3006 LTS version?

[dmurphy18]

@niklasr22 Fixing this on 3006.x branch will get a quicker release than master, also wondering if current test coverage is enough for this change, or does a new test need to be added to cover the code change.

[niklasr22]

@dmurphy18 I opened another PR (#66840) using the 3006.x branch. I also extended an existing test of cmdmod, maybe not the perfect coverage, but better than nothing I guess.

[dwoz]

This will get merged forward from 3006.x into master. See #66840