[BUG] Addreses #3935 and #3683, by making intial_incremental_detokenization_offset configurable

[sinamoeini]

In this PR makes INITIAL_INCREMENTAL_DETOKENIZATION_OFFSET (which had a default value of 5), configurable. This is particularly useful for sentencepiece based tokenizers. For example by setting

intial_incremental_detokenization_offset = 0

Mistral chat API will work as expected

FIX #3935 #3683

[github-actions]

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[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @sinamoeini.

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[sinamoeini]

Can I get a review on this thanks?