[clangd] Update CC Ranking model with better sampling.

A better sampling strategy was used to generate the dataset for this
model.
New signals introduced in this model:
- NumNameInContext: Number of words in the context that matches the name
of the candidate.
- FractionNameInContext: Fraction of the words in context matching the
name of the candidate.

We remove the signal `IsForbidden` from the model and down rank
forbidden signals aggresively.

Differential Revision: https://reviews.llvm.org/D94697