vLLM 5.3+ support

[joerunde]

Description

This PR adds the necessary changes (that I found, at least) to run the adapter with vllm 0.5.3.

The main change was the removal of TextTokensPrompt, it was removed with this PR: vllm-project/vllm@739b61a
I'm not 100% sure if simply replacing with LLMInputs is the correct fix here, but it does seem to work. (I think I see some more complex processing happening on the upstream openai serving engine)

The initializers for all of the OpenAIServing* classes changed, I copied over the new defs from upstream.

Also I noticed that there was no initialization for the tokenizer, so I added it.

How Has This Been Tested?

Booting up a pod with a mig gpu slice, installing vllm@5.3 and vllm-tgis-adapter@llm-inputs, and running the default facebook/opt-125m model with python3 -m vllm_tgis_adapter.

Requests sent using the swagger page at /docs and grpcui (though grpc should be unaffected)

Merge criteria:

• The commits are squashed in a cohesive manner and have meaningful messages.
• Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• The developer has manually tested the changes and verified that the changes work

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 52.00000% with 12 lines in your changes missing coverage. Please review.

Project coverage is 62.73%. Comparing base (0f7df61) to head (60f1ad0).
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/vllm_tgis_adapter/__main__.py	42.85%	11 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #60      +/-   ##
==========================================
- Coverage   62.96%   62.73%   -0.24%     
==========================================
  Files          18       18              
  Lines        1288     1280       -8     
  Branches      229      227       -2     
==========================================
- Hits          811      803       -8     
  Misses        399      399              
  Partials       78       78              

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