Remove IsolatedORTSystem

[jambayk]

Describe your changes

• This system has limited functionality and was added to be able to evaluate qnn models since there was no x64 ort-qnn package available.
• This is not true anymore so the system is not used at all.
• Removing as part of code simplification and easier maintenance.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.
• Is this PR including examples changes? If yes, please remember to update example documentation in a follow-up PR.

(Optional) Issue link