build: Support rebuilding and replacing trtllm backend

[tanmayv25]

What does the PR do?

These changes adds support to rebuild and replace the TRTLLM backend bits with the source held in specified TENSORRTLLM_BACKEND_REPO_TAG.

It can be used like below:

./container/build.sh --framework tensorrtllm --tensorrtllm-backend-rebuild 1 --tensorrtllm-backend-repo-tag tanmayv-v0.16.0

Checklist

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• build
• ci
• docs
• feat
• fix
• perf
• refactor
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• style
• test