🐌 SNPE env and example fix

[trajepl]

Describe your changes

There are a few issues for current SNPE examples:

1. The libxx.so under customized python3.6 need to be put visible for system for SNPE cmd running
   • put str(Path(f"{snpe_root}/python36-env/lib")) under LD_LIBRARY_PATH can fix.
2. SNPE evaluation extent the logits wrongly,
   • fixed in this PR.
3. We did not support tensorflow model evaluation.
   • update examples without input model evaluation.
4. Wrong metrics config for inception examples
5. Importing issue for vgg, tell that in README.md to let user update it manually as a workaround.
6. Python3.6 seems a bit outdated for latest SNPE updates. The vgg example failed to be run. Updated the python env to 3.8 can fix.

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.

(Optional) Issue link

[jambayk]

Thanks for the fixes. The lib and bin paths worked fine previously so I am not sure if it's something to do with the new snpe version or our environment differences. But it doesn't hurt to add extra paths.

[guotuofeng]

It seems the shellcheck fail, do we need fix it?

[guotuofeng]

do we need fix the shellcheck failure?

[trajepl]

do we need fix the shellcheck failure?

Thanks! Added the Shebang info for shell script.