Add Feature "prebuilt-nasm"; Update documentation

[justsmth]

Description of changes:

• Introduce "prebuilt-nasm" feature as requested in previous PR
  • Added documentation about this feature.
• Numerous documentation fixes/updates
• Update User Guide
• Addresses missing documentation identified in: #495

Testing:

• Added CI test for new feature and environment variable.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

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

Project coverage is 92.52%. Comparing base (c358484) to head (fb24403). Report is 78 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #511 +/- ## ========================================== - Coverage 95.80% 92.52% -3.28% ========================================== Files 61 67 +6 Lines 8143 9277 +1134 Branches 0 9277 +9277 ========================================== + Hits 7801 8584 +783 - Misses 342 422 +80 - Partials 0 271 +271 ```

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