Minor fix, use RAII for TensorRT builder and network object

[litaotju]

Description

Both the nvinfer1::INetworkDefinition and nvinfer1::IBuilder class has destroy method to destruct the object, and can use the RAII class InferObject, but original code before this PR does not use this one. This PR enhanced the robustness, espescially when the function throws.

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• The PR title starts with [MXNET-$JIRA_ID], where $JIRA_ID refers to the relevant JIRA issue created (except PRs with tiny changes)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage:
• Unit tests are added for small changes to verify correctness (e.g. adding a new operator)
• Nightly tests are added for complicated/long-running ones (e.g. changing distributed kvstore)
• Build tests will be added for build configuration changes (e.g. adding a new build option with NCCL)
• Code is well-documented:
• For user-facing API changes, API doc string has been updated.
• For new C++ functions in header files, their functionalities and arguments are documented.
• For new examples, README.md is added to explain the what the example does, the source of the dataset, expected performance on test set and reference to the original paper if applicable
• Check the API doc at https://mxnet-ci-doc.s3-accelerate.dualstack.amazonaws.com/PR-$PR_ID/$BUILD_ID/index.html
• To the best of my knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

Changes

• Feature1, tests, (and when applicable, API doc)
• Feature2, tests, (and when applicable, API doc)

Comments

• If this change is a backward incompatible change, why must this change be made.
• Interesting edge cases to note here

[litaotju]

@szha , this is my first commit to this project. Trying to get myself familiar with the project by minor fix. Found I can not request review for this. Do you know what's the proper process for review on such fix? How do I specify reviewers?

(I Saw you name in serveral reviews, so trying to find your help here. Hope you don't mind). Thanks.

[wkcn]

LGTM. Thank you for the contribution!

[wkcn]

Hi @ptrendx , could you please help take a review? Thank you!

[wkcn]

Merged. Thank you!