[V1][Spec Decode][Bugfix] Allocate lookahead token kvc in WAITING queue

[ekagra-ranjan]

FIX #16612

PR #16370 uses num lookahead tokens for computing preallocated kv blocks in EAGLE. However, it skipped for WAITING req which would be req who enter the continous batching for the 1st time or the resumed requests.

[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, @ekagra-ranjan.

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[ekagra-ranjan]

Superseed by: #16941

[WoosukKwon]

@ekagra-ranjan Oh I didn't notice this PR. Apologies 🙏