[Quantization] Add 8-Bit models

[felixdittrich92]

This PR:

• add 8-bit model variants
• add corresponding tests

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 97.44%. Comparing base (48fb2ce) to head (202f994).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #9 +/- ## ========================================== + Coverage 97.43% 97.44% +0.01% ========================================== Files 61 61 Lines 1829 1840 +11 ========================================== + Hits 1782 1793 +11 Misses 47 47 ``` | [Flag](https://app.codecov.io/gh/felixdittrich92/OnnxTR/pull/9/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Felix+Dittrich) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/felixdittrich92/OnnxTR/pull/9/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Felix+Dittrich) | `97.44% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Felix+Dittrich#carryforward-flags-in-the-pull-request-comment) to find out more.

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